Movable body drive method and movable body drive system, pattern formation method and apparatus, exposure method and apparatus, and device manufacturing method

ABSTRACT

Positional information of a wafer stage in a Z-axis direction and a tilt direction with respect to the XY plane (for example, a θy direction) is measured, using a surface position measurement system, such as, for example, a Z head and the like, and the wafer stage is driven based on the measurement results. 
     At the same time, positional information of the wafer stage is measured using an interferometer system such as, for example, a Z interferometer. When abnormality of the surface position measurement system is detected or when the wafer stage moves off from a measurement area of the surface position measurement system, drive control is switched to a drive control based on the measurement results of the interferometer system. Accordingly, the wafer stage can be driven continuously even at the time of abnormality generation in the surface position measurement system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims the benefit of ProvisionalApplication No. 60/935,666 filed Aug. 24, 2007, the disclosure of whichis hereby incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to movable body drive methods and movablebody drive systems, pattern formation methods and apparatuses, exposuremethods and apparatuses, and device manufacturing methods, and moreparticularly, to a movable body drive method and a movable body drivesystem that drives a movable body along a substantially two-dimensionalplane, a pattern formation method using the movable body drive methodand a pattern formation apparatus equipped with the movable body drivesystem, an exposure method using the movable body drive method, and anexposure apparatus equipped with the movable body drive system, and adevice manufacturing method using the pattern formation method.

2. Description of the Background Art

Conventionally, in a lithography process for manufacturing electrondevices (microdevices) such as semiconductor devices (such as integratedcircuits) and liquid crystal display devices, exposure apparatuses suchas a projection exposure apparatus by a step-and-repeat method (aso-called stepper) and a projection exposure apparatus by astep-and-scan method (a so-called scanning stepper (which is also calleda scanner) are mainly used.

However, the surface of a wafer serving as a substrate subject toexposure is not always flat, for example, by undulation and the like ofthe wafer. Therefore, especially in a scanning exposure apparatus suchas a scanner and the like, when a reticle pattern is transferred onto ashot area on a wafer by a scanning exposure method, positionalinformation (surface position information) related to an optical axisdirection of a projection optical system of the wafer surface isdetected at a plurality of detection points set in an exposure area, forexample, using a multiple point focal point position detection system(hereinafter also referred to as a “multipoint AF system”) and the like,and based on the detection results, a so-called focus leveling controlis performed (refer to, for example, U.S. Pat. No. 5,448,332) to controlthe position in the optical axis direction and the inclination of atable (or a stage) holding a wafer so that the wafer surface constantlycoincides with an image plane of the projection optical system in theexposure area (the wafer surface is within the focal depth of the imageplane).

Further, with the stepper or the scanner or the like, wavelength ofexposure light used with finer integrated circuits is becoming shorteryear by year, and numerical aperture of the projection optical system isalso gradually increasing (higher NA), which improves the resolution.Meanwhile, due to shorter wavelength of the exposure light and higher NAin the projection optical system, the depth of focus had becomeextremely small, which caused a risk of focus margin shortage during theexposure operation. Therefore, as a method of substantially shorteningthe exposure wavelength while substantially increasing (widening) thedepth of focus when compared with the depth of focus in the air, theexposure apparatus that uses the immersion method has recently begun togather attention (refer to, for example, the pamphlet of InternationalPublication No. 2004/053955).

However, in the exposure apparatus using this liquid immersion method orother exposure apparatus whose distance (working distance) between thelower end surface of the projection optical system and the wafer issmall, it is difficult to place the multipoint AF system in the vicinityof the projection optical system. Meanwhile, in the exposure apparatus,in order to realize exposure with high precision, realizing surfaceposition control of the wafer with high precision is required.

Further, with the stepper or the scanner or the like, positionmeasurement of the stage (the table) which holds a substrate (forexample, a wafer) subject to exposure was performed in general, using alaser interferometer having a high resolution. However, the optical pathlength of the laser interferometry beam which measures the position ofthe stage is around several hundred mm or more, and furthermore, due tofiner patterns owing to higher integration of semiconductor devices,position control of the stage with higher precision is becomingrequired. Therefore, short-term variation of measurement values which iscaused by air fluctuation which occurs due to the influence oftemperature fluctuation or temperature gradient of the atmosphere on thebeam optical path of the laser interferometer can no longer be ignored.

Therefore, it can be considered that position control of the table inthe optical axis direction and in a tilt direction with respect to thesurface orthogonal to the optical axis, including the focus levelingcontrol of the wafer during exposure, using a detection device whichdetects the surface position information of the table, is to beperformed together with the interferometer. However, in such a case,countermeasures against times such as sudden output abnormality of thedetection device are required.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda first movable body drive method in which a movable body is drivensubstantially along a two-dimensional planet the method comprising: afirst process in which positional information of the movable bodyrelated to at least one of a direction perpendicular to thetwo-dimensional plane and a tilt direction with respect to thetwo-dimensional plane is detected, using a first detection device thathas one, or more than one detection positions placed in at least a partof an operating area of the movable body, and detects positionalinformation of the movable body in the direction perpendicular to thetwo-dimensional plane using detection information detected when themovable body is positioned at any one of the detection points, and asecond detection device that detects positional information of themovable body in the direction perpendicular to the two-dimensional planefrom measurement results using a measurement beam irradiated along thetwo-dimensional plane between the outside of the operating area of themovable body and the movable body, and the movable body is driven in atleast one of the direction perpendicular to the two-dimensional planeand the tilt direction with respect to the two-dimensional plane basedon detection results of the first detection device; a second process inwhich relation information between a first positional information of themovable body computed from detection information of the first detectiondevice and a second positional information of the movable body computedfrom detection information of the second detection device is updated atevery predetermined timing; and a third process in which whenabnormality occurring in an output of the first detection device hasbeen detected, the detection device used for drive control of themovable body in at least one of the direction perpendicular to thetwo-dimensional plane and the tilt direction with respect to thetwo-dimensional plane is switched from the first detection device to thesecond detection device.

According to this method, when abnormality occurring in the output ofthe first detection device has been detected, the detection device usedfor drive control of at least one of the direction perpendicular to thetwo-dimensional plane and the tilt direction with respect to thetwo-dimensional plane is switched from the first detection device to thesecond detection device. Accordingly, backup by the second detectiondevice in which output abnormality is remarkably hard to occur whencompared with the first detection device from the measurement principle,becomes possible at the time of generation of output abnormality in thefirst detection device.

According to a second aspect of the present invention, there is provideda second movable body drive method in which a movable body is drivensubstantially along a two-dimensional plane, the method comprising: afirst process in which positional information of the movable body indirections of three degrees of freedom within a plane parallel to thetwo-dimensional plane is detected, using a first detection device whichdetects positional information in directions of three degrees of freedomwithin the plane parallel to the two-dimensional plane from measurementresults using a measurement beam irradiated along the two-dimensionalplane between the outside of the operating area of the movable body andthe movable body, and positional information of the movable body in adirection perpendicular to the two-dimensional plane and a tiltdirection with respect to the two-dimensional plane is also detected,using a second detection device which detects positional information ofthe movable body in a direction perpendicular to the two-dimensionalplane and a tilt direction with respect to the two-dimensional planefrom measurement results using a measurement beam irradiated along thetwo-dimensional plane between the outside of the operating area of themovable body and the movable body; and a second process in which onswitching from servo control of the position in the directions of threedegrees of freedom of the movable body using the first detection deviceto servo control of the position in the directions of three degrees offreedom of the movable body using an encoder system, a detection devicethat detects positional information of the movable body in the directionperpendicular to the two-dimensional plane and the tilt direction aroundat least one axis with respect to the two-dimensional plane is switchedfrom the second detection device when the movable body is in a suspendedstate, to a third detection device that has a plurality of detectionpositions placed in at least a part of an operating area of the movablebody, and detects positional information of the movable body in thedirection perpendicular to the two-dimensional plane using detectioninformation detected when the movable body is positioned at any one ofthe detection positions.

According to this method, the detection device which detects positionalinformation of the movable body in the direction perpendicular to thetwo-dimensional plane and the tilt direction around at least one axiswith respect to the two-dimensional plane is switched from the seconddetection device when the movable body is in a suspended state to thethird detection device, on switching from servo control of the positionin the directions of three degrees of freedom of the movable body usingthe first detection device to servo control of the position in thedirections of three degrees of freedom of the movable body using theencoder system. Because the switching from the second detection deviceto the third detection device is performed with the movable body in asuspended state as described above, even if discontinuity occurs betweenthe position of the movable body related to the direction perpendicularto the two-dimensional plane and the tilt direction around at least oneaxis with respect to the two-dimensional plane computed by the seconddetection device and the position of the movable body related to thedirection perpendicular to the two-dimensional plane and the tiltdirection around at least one axis with respect to the two-dimensionalplane computed by the third detection device before and after theswitching, switching from the second detection device to the thirddetection device can be performed without any trouble.

According to a third aspect of the present invention, there is provideda third movable body drive method in which a movable body is drivensubstantially along a two-dimensional plane, the method comprising: afirst process in which the movable body is driven based on an output ofa first detection device that has a plurality of detection positionsplaced in at least a part of an operating area of the movable body, anddetects positional information of the movable body in a directionperpendicular to the two-dimensional plane using detection informationdetected when the movable body is positioned at any one of the detectionpositions, and the output of an encoder system that measures positionalinformation of the movable body within a plane parallel to thetwo-dimensional plane in directions of three degrees of freedom; and asecond process in which in the case of switching from servo control ofthe position of the movable body in the directions of three degrees offreedom using the encoder system, to a control of the position of themovable body in the directions of three degrees of freedom using asecond detection device that detects positional information indirections of three degrees of freedom within a plane parallel to thetwo-dimensional plane from measurement results using a measurement beamirradiated along the two-dimensional plane between the outside of theoperating are of the movable body and the movable body, a detectiondevice used for control of the position of the movable body in theremaining directions of three degrees of freedom is switched from thefirst detection device to a third detection device that detectspositional information of the movable body in the directionperpendicular to the two-dimensional plane and a tilt direction withrespect to the two-dimensional plane from measurement results using ameasurement beam irradiated along the two-dimensional plane between theoutside of the operating area of the movable body and the movable bodyat the point where the movable body is suspended.

According to this method, in the case of switching from servo control ofthe position of the movable body in the directions of three degrees offreedom using the encoder system, to a control of the position of themovable body in the directions of three degrees of freedom using asecond detection device, the detection device used for control of theremaining directions of three degrees of freedom is switched from thefirst detection device to the third detection device at the point wherethe movable body is suspended. Because the switching from the firstdetection device to the third detection device is performed at the pointwhere the movable body is suspended in the manner described above, theswitching from the first detection device to the third detection devicecan be performed without any trouble in particular, even ifdiscontinuity occurs in the computed position of the movable body beforeand after the switching.

According to a fourth aspect of the present invention, there is provideda pattern formation method to form a pattern on an object wherein amovable body on which the object is mounted is driven using any one ofthe first to third movable body drive method of the present invention toperform pattern formation to the object.

According to this method, by forming a pattern on the object mounted onthe movable body which is driven using one of the first to third movablebody drive methods of the present invention, it becomes possible to forma pattern on the object with good accuracy.

According to a fifth aspect of the present invention, there is provideda device manufacturing method including a pattern formation processwherein in the pattern formation process, a pattern is formed on asubstrate using the pattern formation method of the present invention.

According to a sixth aspect of the present invention, there is providedan exposure method in which a pattern is formed on an object by anirradiation of an energy beam wherein for relative movement of theenergy beam and the object, a movable body on which the object ismounted is driven, using one of the first to third movable body drivemethods of the present invention.

According to this method, for relative movement of the energy beamirradiated on the object and the object, the movable body on which theobject is mounted is driven with good precision, using one of the firstto third movable body drive methods of the present invention.Accordingly, it becomes possible to form a pattern on the object withgood precision by scanning exposure.

According to a seventh aspect of the present invention, there isprovided a first movable body drive system in which a movable body isdriven substantially along a two-dimensional plane, the systemcomprising: a first detection device that has at least one detectionposition placed in at least a part of an operating area of the movablebody, and detects positional information of the movable body in adirection perpendicular to the two-dimensional plane using detectioninformation detected when the movable body is positioned at any one ofthe detection points; a second detection device that detects positionalinformation of the movable body in the direction perpendicular to thetwo-dimensional plane from measurement results using a measurement beamirradiated along the two-dimensional plane between the outside of theoperating area of the movable body and the movable body; and acontroller that drives the movable body at least one of a directionperpendicular to the two-dimensional plane and a tilt direction withrespect to the two-dimensional plane based on detection results of thefirst detection device, and also updates relation information between afirst positional information computed from detection information of thefirst detection device and a second positional information computed fromdetection information of the second detection device at everypredetermined timing, and when abnormality occurring in the output ofthe first detection device is detected, switches a detection device usedfor drive control of at least one of the direction perpendicular to thetwo-dimensional plane and a tilt direction with respect to thetwo-dimensional plane from the first detection device to the seconddetection device.

According to this system, when abnormality occurring in the output ofthe first detection device is detected by the controller, the detectiondevice used for drive control of the movable body in at least one of thedirection perpendicular to the two-dimensional plane and the tiltdirection with respect to the two-dimensional plane is switched from thefirst detection device to the second detection device. Accordingly,backup by the second detection device in which output abnormality isremarkably hard to occur when compared with the first detection devicefrom the measurement principle, becomes possible at the time ofgeneration of output abnormality in the first detection device.

According to an eighth aspect of the present invention, there isprovided a second movable body drive system in which a movable body isdriven along a substantially two-dimensional plane, the systemcomprising: a first detection device that has a plurality of detectionpositions placed in at least a part of an operating area of the movablebody, and detects positional information of the movable body in adirection perpendicular to the two-dimensional plane using detectioninformation detected when the movable body is positioned at any one ofthe detection points; an encoder system that measures positionalinformation of the movable body in directions of three degrees offreedom; a second detection device that detects positional informationof the movable body in directions of three degrees of freedom within aplane parallel to the two-dimensional plane from measurement resultsusing a measurement beam irradiated along the two-dimensional planebetween the outside of the operating area of the movable body and themovable body; a third detection device that detects positionalinformation of the movable body in a direction perpendicular to thetwo-dimensional plane and a tilt direction with respect to thetwo-dimensional plane from measurement results using a measurement beamirradiated along the two-dimensional plane between the outside of theoperating area of the movable body and the movable body; and acontroller that switches a detection device which detects positionalinformation of the movable body in the direction perpendicular to thetwo-dimensional plane and the tilt direction around at least one axiswith respect to the two-dimensional plane from the third detectiondevice when the movable body is in a suspended state to the firstdetection device, on switching from servo control of the position in thedirections of three degrees of freedom of the movable body using thesecond detection device to servo control of the position in thedirections of three degrees of freedom of the movable body using theencoder system.

According to this system, because the switching from the seconddetection device to the third detection device is performed with themovable body in a suspended state as described above, even ifdiscontinuity occurs between the position of the movable body related tothe direction perpendicular to the two-dimensional plane and the tiltdirection around at least one axis with respect to the two-dimensionalplane computed by the first detection device and the position of themovable body related to the direction perpendicular to thetwo-dimensional plane and the tilt direction around at least one axiswith respect to the two-dimensional plane computed by the thirddetection device before and after the switching, switching from thesecond detection device to the third detection device can be performedwithout any trouble.

According to a ninth aspect of the present invention, there is provideda third movable body drive system in which a movable body is drivenalong a substantially two-dimensional plane, the system comprising: afirst detection device that has a plurality of detection positionsplaced in at least a part of an operating area of the movable body, anddetects positional information of the movable body in a directionperpendicular to the two-dimensional plane using detection informationdetected when the movable body is positioned at any one of the detectionpoints; an encoder system that measures positional information of themovable body within a plane parallel to the two-dimensional plane indirections of three degrees of freedom; a second detection device thatdetects positional information of the movable body in directions ofthree degrees of freedom within a plane parallel to the two-dimensionalplane from measurement results using a measurement beam irradiated alongthe two-dimensional plane between the outside of the operating area ofthe movable body and the movable body; a third detection device thatdetects positional information of the movable body in a directionperpendicular to the two-dimensional plane and a tilt direction withrespect to the two-dimensional plane from measurement results using ameasurement beam irradiated along the two-dimensional plane between theoutside of the operating area of the movable body and the movable body;and a controller that switches a measurement device used for controllingthe position of the movable body in the remaining directions of threedegrees of freedom from the first detection device to the thirddetection device at the point where the movable body is suspended, inthe case of switching from servo control of the position of the movablebody using the encoder system to control of the position of the movablebody in the directions of three degrees of freedom using the seconddetection device.

According to this system, because the switching from the first detectiondevice to the third detection device is performed at the point where themovable body is suspended in the manner described above, the switchingfrom the first detection device to the third detection device can beperformed without any trouble in particular, even if discontinuityoccurs in the computed position of the movable body before and after theswitching.

According to a tenth aspect of the present invention, there is provideda pattern forming apparatus that forms a pattern on an objects theapparatus comprising: a patterning device which generates a pattern onthe object; and one of the first to third movable body drive systems ofthe present invention, wherein drive of a movable body on which theobject is mounted is performed by the movable body drive system forpattern formation with respect to the object.

According to this apparatus, by generating a pattern with a patterningunit on the object on the movable body driven with good precision by anyone of the first to third movable body drive systems of the presentinvention, it becomes possible to form a pattern on the object with goodprecision.

According to an eleventh aspect of the present invention, there isprovided an exposure apparatus that forms a pattern on an object by anirradiation of an energy beam, the apparatus comprising: a patterningdevice that irradiates the energy beam on the object; and one of thefirst to third movable body drive systems of the present invention,wherein the movable body drive system drives the movable body on whichthe object is mounted for relative movement of the energy beam and theobject.

According to this apparatus, for relative movement of the energy beamirradiated on the object from the patterning unit and the object, themovable body on which the object is mounted is driven with goodprecision by one of the first and second movable body drive system ofthe present invention. Accordingly, it becomes possible to form apattern on the object with good precision by scanning exposure.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings;

FIG. 1 is a view that schematically shows a configuration of an exposureapparatus of an embodiment;

FIG. 2 is a planar view showing a stage device in FIG. 1;

FIG. 3 is planar view showing placement of various measurement device(an encoder, alignment system, multipoint AF system, a Z head) whichexposure apparatus of FIG. 1 comprises;

FIG. 4A is a planar view showing a wafer stage, and FIG. 4B is aschematic side view of a partially sectioned wafer stage WST;

FIG. 5A is a planar view that shows a measurement stage MST, and FIG. 5Bis a partially sectioned schematic side view that shows measurementstage MST;

FIG. 6 is a block diagram showing a configuration of a control system ofthe exposure apparatus related to an embodiment.

FIG. 7 is a view schematically showing an example of a configuration ofa Z head;

FIG. 8A is a view showing an example of a focus sensor, FIGS. 8B and 8Care views used to explain the shape and function of a cylindrical lensin FIG. 8A;

FIG. 9A is a view showing a divided state of a detection area of atetrameric light receiving element, FIGS. 5B, 5C, and 9D are viewsrespectively showing a cross-sectional shape of reflected beam LB₂ on adetection surface in a front-focused, an ideal focus, and a back-focusedstate;

FIGS. 10A to 10C are views used to explain focus mapping performed inthe exposure apparatus of an embodiment;

FIGS. 11A and 11B are views used to explain focus calibration performedin the exposure apparatus of an embodiment;

FIGS. 12A and 12B are views used to explain offset correction among AFsensors performed in the exposure apparatus related to an embodiment;

FIG. 13 is a view showing a state of the wafer stage and the measurementstage where exposure to a water on the wafer stage is performed by astep-and-scan method;

FIG. 14 is a view showing a state of both stages at the time ofunloading of the wafer (when the measurement stage reaches the positionwhere Sec-BCHK (interval) is performed);

FIG. 15 is a view showing a state of both stages at the time of loadingof the wafer;

FIG. 16 is a view showing a state of both stages at the time ofswitching (when the wafer stage has moved to a position where the formerprocessing of Pri-BCHK is performed) from stage servo control by theinterferometer to stage servo control by the encoder;

FIG. 17 is a view showing a state of the wafer stage and the measurementstage when alignment marks arranged in three first alignment shot areasare being simultaneously detected using alignment systems AL1, AL2 ₂ andAL2 ₃;

FIG. 18 is a view showing a state of the wafer stage and the measurementstage when the former processing of focus calibration is beingperformed;

FIG. 19 is a view showing a state of the wafer stage and the measurementstage when alignment marks arranged in five second alignment shot areasare being simultaneously detected using alignment systems AL1 and AL2 ₁to AL2 ₄;

FIG. 20 is a view showing a state of the wafer stage and the measurementstage when at least one of the latter processing of Pri-BCHK and thelatter processing of focus calibration is being performed;

FIG. 21 is a view showing a state of the wafer stage and the measurementstage when alignment marks arranged in five third alignment shot areasare being simultaneously detected using alignment systems AL1 and AL2 ₁to AL2 ₄;

FIG. 22 is a view showing a state of the wafer stage and the measurementstage when alignment marks arranged in three fourth alignment shot areasare being simultaneously detected using alignment systems AL1, AL2 ₂ andAL2 ₃;

FIG. 23 is a view showing a state of the wafer stage and the measurementstage when the focus mapping has ended;

FIGS. 24A and 24B are views for explaining a computation method of the Zposition and the amount of tilt of the wafer stage using the measurementresults of the Z heads;

FIGS. 25A and 253 are views showing the state of a switching of the Zheads which oppose the Y scale, along with the movement of the waferstage;

FIGS. 26A to 26E are views for explaining the switching procedure of theZ heads;

FIGS. 27A to 27C are views for explaining a return procedure of the Zheads using two states, which are scale servo and focus servo;

FIGS. 28A and 28B are views for explaining a switching process of the Zheads used for position control of the wafer stage;

FIG. 29 is a view conceptually showing position control of the waferstage, uptake of a measurement value of the Z head, and the switchingtiming of the Z head;

FIGS. 30A to 30H are views to explain a handling procedure at the timeof temporary abnormality output of the Z head, using the two states,which are scale servo and focus servo; and

FIG. 31 is a view showing an outline of a linkage process in a switchingto servo drive control of the wafer stage, from the Z head system to theinterferometer system, and the interferometer system to the Z headsystem.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described,referring to FIGS. 1 to 31.

FIG. 1 shows a schematic configuration of an exposure apparatus 100 inthe embodiment. Exposure apparatus 100 is a scanning exposure apparatusof the step-and-scan method, namely the so-called scanner. As it will bedescribed later, a projection optical system PL is arranged in theembodiment, and in the description below, a direction parallel to anoptical axis AX of projection optical system PL will be described as theZ-axis direction, a direction within a plane orthogonal to the Z-axisdirection in which a reticle and a water are relatively scanned will bedescribed as the Y-axis direction, a direction orthogonal to the Z-axisand the Y-axis will be described as the X-axis direction, and rotational(inclination) directions around the X-axis, the Y-axis, and the Z-axiswill be described as θx, θy, and θz directions, respectively.

Exposure apparatus 100 is equipped with an illumination system 10, areticle stage RST that holds a reticle R that is illuminated by anillumination light for exposure (hereinafter, ref erred to asillumination light, or exposure light) IL from illumination system 10, aprojection unit PU that includes projection optical system PL thatprojects illumination light IL emitted from reticle R on a wafer W, astage device 50 that has a wafer stage WST and a measurement stage MST,their control system, and the like. On wafer stage WST, wafer W ismounted.

Illumination system 10 includes a light source, an illuminanceuniformity optical system, which includes an optical integrator and thelike, and an illumination optical system that has a reticle blind andthe like (none of which are shown), as is disclosed in, for example,U.S. Patent Application Publication No. 2003/0025090 and the like.Illumination system 10 illuminates a slit-shaped illumination area IARwhich is set on reticle R with a reticle blind (a masking system) byillumination light (exposure light) IL with a substantially uniformilluminance. In this case, as illumination light IL, for example, an ArFexcimer laser beam (wavelength 193 nm) is used. Further, as the opticalintegrator, for example, a fly-eye lens, a rod integrator (an internalreflection type integrator), a diffractive optical element or the likecan be used.

On reticle stage RST, reticle R on which a circuit pattern or the likeis formed on its pattern surface (the lower surface in FIG. 1) is fixed,For example, by vacuum chucking. Reticle stage RST is finely drivable ormovable in within an XY plane by a reticle stage drive section 11 (notshown in FIG. 1, refer to FIG. 6) that includes a linear motor or thelike, and reticle stage RST is also drivable in a scanning direction (inthis case, the Y-axis direction, which is the lateral direction of thepage surface in FIG. 1) at a designated scanning speed.

The positional information (including position (rotation) information inthe θz direction) of reticle stage RST in the XY plane (movement plane)is constantly detected, for example, at a resolution of around 0.25 nmby a reticle laser interferometer (hereinafter referred to as a “reticleinterferometer”) 116, via a movable mirror 15 (the mirrors actuallyarranged are a Y movable mirror (or a retro reflector) that has areflection surface which is orthogonal to the Y-axis direction and an Xmovable mirror that has a reflection surface orthogonal to the X-axisdirection). The measurement values of reticle interferometer 116 aresent to a main controller 20 (not shown in FIG. 17 refer to FIG. 6).Main controller 20 computes the position of reticle stage RST in theX-axis direction, Y-axis direction, and the θz direction based on themeasurement values of reticle interferometer 116, and also controls theposition (and velocity) of reticle stage RST by controlling reticlestage drive section 11 based on the computation results. Incidentally,instead of movable mirror 15, the edge surface of reticle stage RSV canbe mirror polished so as to form a reflection surface (corresponding tothe reflection surface of movable mirror 15). Further, reticleinterferometer 116 can measure positional information of reticle stageRST related to at least one of the Z-axis, θx, or θy directions.

Projection unit PU is placed below reticle stage RST in FIG. 1.Projection unit PU includes a barrel 40, and projection optical systemPL that has a plurality of optical elements which are held in apredetermined positional relation inside barrel 40. As projectionoptical system PL, for example, a dioptric system is used, consisting ofa plurality of lenses (lens elements) that is disposed along an opticalaxis AX, which is parallel to the Z-axis direction. Projection opticalsystem PL is, for example, a both-side telecentric dioptric system thathas a predetermined projection magnification (such as one-quarter,one-fifth, or one-eighth times). Therefore, when illumination light ILfrom illumination system 10 illuminates illumination area TARP a reducedimage of the circuit pattern (a reduced image of a part of the circuitpattern) of the reticle is formed within illumination area IAR, withillumination light IL that has passed through reticle R which is placedso that its pattern surface substantially coincides with a first plane(an object plane) of projection optical system PL, in an area conjugateto illumination area IAR on wafer W (exposure area) whose surface iscoated with a resist (a photosensitive agent) and is placed on a secondplane (an image plane) side, via projection optical system PL(projection unit PU). And by reticle stage RST and wafer stage WST beingsynchronously driven, the reticle is relatively moved in the scanningdirection (the Y-axis direction) with respect to illumination area IAR(illumination light IL) while wafer W is relatively moved in thescanning direction (the Y-axis direction) with respect to the exposurearea (illumination light IL), thus scanning exposure of a shot area(divided area) on wafer W is performed, and the pattern of the reticleis transferred onto the shot area. That is, in the embodiment, thepattern is generated on wafer W according to illumination system 10, thereticle, and projection optical system PL, and then by the exposure ofthe sensitive layer (resist layer) on wafer W with illumination lightIL, the pattern is formed on wafer W.

Incidentally, although it is not shown, projection unit PU is installedin a barrel platform supported by three struts via a vibration isolationmechanism. However, as well as such a structure, as is disclosed in, forexample, the pamphlet of International Publication WO2006/038952 and thelike, projection unit PU can be supported by suspension with respect toa mainframe member (not shown) placed above projection unit PU or withrespect to a base member on which reticle stage RST is placed.

Incidentally, in exposure apparatus 100 of the embodiment, becauseexposure is performed applying a liquid immersion method, an opening onthe reticle side becomes larger with the substantial increase of thenumerical aperture NA. Therefore, in order to satisfy Petzval'scondition and to avoid an increase in size of the projection opticalsystem, a reflection/refraction system (a catodioptric system) which isconfigured including a mirror and a lens can be employed as a projectionoptical system. Further, in wafer W, in addition to a sensitive layer (aresist layer), for example, a protection film (a topcoat film) or thelike which protects the wafer or a photosensitive layer can also beformed.

Further, in exposure apparatus 100 of the embodiment, in order toperform exposure applying the liquid immersion method, a nozzle unit 32that constitutes part of a local liquid immersion device 8 is arrangedso as to enclose the periphery of the lower end portion of barrel 40that holds an optical element that is closest to an image plane side(wafer W side) that constitutes projection optical system PL, which is alens (hereinafter, also referred to a “tip lens”) 191 in this case. Inthe embodiment, as shown in FIG. 1, the lower end surface of nozzle unit32 is set to be substantially flush with the lower end surface of tiplens 191. Further, nozzle unit 32 is equipped with a supply opening anda recovery opening of liquid Lq, a lower surface to which wafer W isplaced facing and at which the recovery opening is arranged, and asupply flow channel and a recovery flow channel that are connected to aliquid supply pipe 31A and a liquid recovery pipe 31B respectively.Liquid supply pipe 31A and liquid recovery pipe 31B are slanted byaround 45 degrees relative to an X-axis direction and Y-axis directionin a planar view (when viewed from above) as shown in FIG. 3, and areplaced symmetric to a straight line (a reference axis) LV which passesthrough the center (optical axis AX of projection optical system PL,coinciding with the center of exposure area IA previously described inthe embodiment) of projection unit PU and is also parallel to theY-axis.

One end of a supply pipe (not shown) is connected to liquid supply pipe31A while the other end of the supply pipe is connected to a liquidsupply unit 5 (not shown in FIG. 1, refer to FIG. 6), and one end of arecovery pipe (not shown) is connected to liquid recovery pipe 313 whilethe other end of the recovery pipe is connected to a liquid recoverydevice 6 (not shown in FIG. 1, refer to FIG. 6).

Liquid supply device 5 includes a liquid tank for supplying liquid, acompression pump, a temperature controller, a valve for controllingsupply/stop of the liquid to liquid supply pipe 31A, and the like. Asthe valve, for example, a flow rate control valve is preferably used sothat not only the supply/stop of the liquid but also the adjustment offlow rate can be performed. The temperature controller adjusts thetemperature of the liquid within the tanks for example, to nearly thesame temperature as the temperature within the chamber (not shown) wherethe exposure apparatus is housed. Incidentally, the tank, thecompression pump, the temperature controller, the valve, and the like donot all have to be equipped in exposure apparatus 100, and at least partof them can also be substituted by the equipment or the like availablein the plant where exposure apparatus 100 is installed.

Liquid recovery device 6 includes a liquid tank for collecting liquid, asuction pump, a valve for controlling recovery/stop of the liquid vialiquid recovery pipe 31B, and the like. As the valve, it is desirable touse a flow control valve similar to the valve of liquid supply device 5.Incidentally, the tank, the suction pump, the valve, and the like do notall have to be equipped in exposure apparatus 100, and at least part ofthem can also be substituted by the equipment or the like available inthe plants where exposure apparatus 100 is installed.

In the embodiment, as liquid Lq described above, pure water(hereinafter, it will simply be referred to as “water” besides the casewhen specifying is necessary) that transmits the ArF excimer laser light(light with a wavelength of 193 nm) is to be used. Pure water can beobtained in large quantities at a semiconductor manufacturing plant orthe like without difficulty, and it also has an advantage of having noadverse effect on the photoresist on the wafer, to the optical lenses orthe like.

Refractive index n of the water with respect to the ArF excimer laserlight is around 1.44. In the water the wavelength of illumination lightIL is 193 nm×1/n, shorted to around 134 nm.

Liquid supply device 5 and liquid recovery device 6 each, have acontroller, and the respective controllers are controlled by maincontroller 20 (refer to FIG. 6). According to instructions from maincontroller 20, the controller of liquid supply device 5 opens the valveconnected to liquid supply pipe 31A to a predetermined degree to supplyliquid (water) to the space between tip lens 191 and wafer w via liquidsupply pipe 31A, the supply flow channel and the supply opening.Further, when the water is supplied, according to instructions from maincontroller 20, the controller of liquid recovery device 6 opens thevalve connected to liquid recovery pipe 31B to a predetermined degree torecover the liquid (water) from the space between tip lens 191 and waterW into liquid recovery device 6 (the liquid tank) via the recoveryopening, the recovery flow channel and liquid recovery pipe 31B. Duringthe supply and recovery operations, main controller 20 gives commands tothe controllers of liquid supply device 5 and liquid recovery device 6so that the quantity of water supplied to the space between tip lens 191and wafer W constantly equals the quantity of water recovered from thespace. Accordingly, a constant quantity of liquid (water) Lq (refer toFIG. 1) is held in the space between tip lens 191 and wafer W. In thiscase, liquid (water) Lq held in the space between tip lens 191 and waferW is constantly replaced.

As is obvious from the above description, in the embodiment, localliquid immersion device 8 is configured including nozzle unit 32, liquidsupply device 5, liquid recovery device 6, liquid supply pipe 31A andliquid recovery pipe 31B, and the like. Incidentally, part of localliquid immersion device 8, for example, at least nozzle unit 32 may alsobe supported in a suspended state by a main frame (including the barrelplatform) that holds projection unit PU, or may also be arranged atanother frame member that is separate from the main frame. Or, in thecase projection unit PU is supported in a suspended state as isdescribed earlier, nozzle unit 32 may also be supported in a suspendedstate integrally with projection unit PU, but in the embodiment, nozzleunit 32 is arranged on a measurement frame that is supported in asuspended state independently from projection unit PU. In this case,projection unit PU does not have to be supported in a suspended state.

Incidentally, also in the case measurement stage MST is located belowprojection unit PU, the space between a measurement table (to bedescribed later) and tip lens 191 can be Filled with water in thesimilar manner to the manner described above.

Incidentally, in the description above, one liquid supply pipe (nozzle)and one liquid recovery pipe (nozzle) were arranged as an example,however, the present invention is not limited to this, and aconfiguration having multiple nozzles as is disclosed in, for example,the pamphlet of International Publication No 99/49504, may also beemployed, in the case such an arrangement is possible taking intoconsideration a relation with adjacent members. The point is that anyconfiguration can be employed, as long as the liquid can be supplied inthe space between optical member (tip lens) 191 in the lowest endconstituting projection optical system PL and wafer W. For example, theliquid immersion mechanism disclosed in the pamphlet of InternationalPublication No. 2004/053955, or the liquid immersion mechanism disclosedin the EP Patent Application Publication No. 1 420 298 can also beapplied to the exposure apparatus of the embodiment.

Referring back to FIG. 1, stage device 50 is equipped with a wafer stageWST and a measurement stage MST placed above a base board 12, ameasurement system 200 (refer to FIG. 6) which measures positionalinformation of the stages WST and MST, a stage drive system 124 (referto FIG. 6) which drives stages WST and MST and the like. Measurementsystem 200 includes an interferometer system 118, an encoder system 150,and a surface position measurement system 180 and the like as shown inFIG. 6. Incidentally, details on interferometer system 118, encodersystem 150 and the like will be described later in the description.

Referring back to FIG. 1, on the bottom surface of each of wafer stageWST and measurement stage MST, a noncontact bearing (not shown), forexample, a vacuum preload type hydrostatic air bearing (hereinafter,referred to as an “air pad”) is arranged at a plurality of points, andwafer stage WST and measurement stage MST are supported in a noncontactmanner via a clearance of around several μm above base board 12, bystatic pressure of pressurized air that is blown out from the air padtoward the upper surface of base board 12. Further, stages WST and MSTare drivable independently within the XY plane, by stage drive system124 (refer to FIG. 6) which includes a linear motor and the like.

Wafer stage WST includes a stage main section 91, and a wafer table WTBthat is mounted on stage main section 91. Wafer table WTB and stage mainsection 91 are configured drivable in directions of six degrees offreedom (X, Y, Z, θx, θy, and θz) with respect to base board 12 by adrive system including a linear motor and a Z leveling mechanism (forexample, including a voice coil motor and the like).

On wafer table WTB, a wafer holder (not shown) that holds wafer W byvacuum suction or the like is arranged. The wafer holder may also beformed integrally with wafer table WTB, but in the embodiment, the waferholder and wafer table WTB are separately configured, and the waferholder is fixed inside a recessed portion of wafer table WTB, forexample, by vacuum suction or the like. Further, on the upper surface ofwafer table WTB, a plate (liquid repellent plate) 28 is arranged, whichhas the surface (liquid repellent surface) substantially flush with thesurface of wafer W mounted on the wafer holder to which liquid repellentprocessing with respect to liquid Lq is performed, has a rectangularouter shape (contour), and has a circular opening that is formed in thecenter portion and is slightly larger than the wafer holder (a mountingarea of the wafer). Plate 28 is made of materials with a low coefficientof thermal expansion, such as glass or ceramics (e.g., such as Zerodur(the brand name) of Schott AG, Al₂O₃, or Tic), and on the surface ofplate 28, a liquid repellent film is formed by, for example, fluorineresin materials, fluorine series resin materials such aspolytetrafluoroethylene (Teflon (registered trademark)), acrylic resinmaterials, or silicon series resin materials. Further, as shown in aplaner view of wafer table WTB (wafer stage WST) in FIG. 4A, plate 28has a first liquid repellent area 28 a whose outer shape (contour) isrectangular enclosing a circular opening, and a second liquid repellentarea 28 b that has a rectangular frame (annular) shape placed around thefirst liquid repellent area 28 a. On the first liquid repellent area 28a, for example, at the time of an exposure operation, at least part of aliquid immersion area 14 (refer to FIG. 13) that is protruded from thesurface of the wafer is formed, and on the second liquid repellent area28 b, scales for an encoder system (to be described later) are formed.Incidentally, at least part of the surface of plate 28 does not have tobe on a flush surface with the surface of the wafer, that is, may have adifferent height from that of the surface of the wafer. Further, plate28 may be a single plate, but in the embodiment, plate 28 is configuredby combining a plurality of plates, for example, the first and secondliquid repellent plates that correspond to the first liquid repellentarea 28 a and the second liquid repellent area 28 b respectively. In theembodiment, water is used as liquid Lq as is described above, andtherefore, hereinafter the first liquid repellent area 28 a and thesecond liquid repellent area 28 b are also referred to as a first waterrepellent plate 28 a and a second water repellent plate 28 b.

In this case, while exposure light IL is irradiated to the first waterrepellent plate 28 a on the inner side, exposure light IL is hardlyirradiated to the second water repellent plate 28 b on the outer side.Taking this fact into consideration, in the embodiment, a first waterrepellent area to which water repellent coat having sufficientresistance to exposure light IL (light in a vacuum ultraviolet region,in this case) is applied is formed on the surface of the first waterrepellent plate 28 a, and a second water repellent area to which waterrepellent coat having resistance to exposure light IL inferior to thefirst water repellent area is applied is formed on the surface of thesecond water repellent plate 28 b. In general, since it is difficult toapply water repellent coat having sufficient resistance to exposurelight IL (in this case, light in a vacuum ultraviolet region) to a glassplate, it is effective to separate the water repellent plate into twosections, the first water repellent plate 28 a and the second waterrepellent plate 28 b which is the periphery of the first water repellentplate, in the manner described above. Incidentally, the presentinvention is not limited to this, and two types of water repellent coatthat have different resistance to exposure light IL may also be appliedon the upper surface of the same plate in order to form the first waterrepellent area and the second water repellent area. Further, the samekind of water repellent coat may be applied to the first and secondwater repellent areas. For example, only one water repellent area mayalso be formed on the same plate.

Further, as is obvious from FIG. 4A, at the end portion on the +Y sideof the first water repellent plate 28 a, a rectangular cutout is formedin the center portion in the X-axis direction, and a measurement plate30 is embedded inside the rectangular space (inside the cutout) that isenclosed by the cutout and the second water repellent plate 28 b. Afiducial mark FM is formed in the center in the longitudinal directionof measurement plate 30 (on a centerline LL of wafer table WTB), and apair of aerial image measurement slit patterns (slit-shaped measurementpatterns) SL are formed in the symmetrical placement with respect to thecenter of the fiducial mark on one side and the other side in the X-axisdirection of fiducial mark FM. As each of aerial image measurement slitpatterns SL, an L-shaped slit pattern having sides along the Y-axisdirection and X-axis direction, or two linear slit patterns extending inthe X-axis and Y-axis directions respectively can be used, as anexample.

Further, as is shown in FIG. 4B, inside wafer stage WST below each ofaerial image measurement slit patterns SL, an L-shaped housing 36 inwhich an optical system containing an objective lens, a mirror, a relaylens and the like is housed is attached in a partially embedded statepenetrating through part of the inside of wafer table WTB and stage mainsection 91. Housing 36 is arranged in pairs corresponding to the pair ofaerial image measurement slit patterns SL, although omitted in thedrawing.

The optical system inside housing 36 guides illumination light IL thathas been transmitted through aerial image measurement slit pattern SLalong an L-shaped route and emits the light toward a −Y direction.Incidentally, in the following description, the optical system insidehousing 36 is described as a light-transmitting system 36 by using thesame reference code as housing 36 for the sake of convenience.

Moreover, on the upper surface of the second water repellent plate 28 b,multiple grid lines are directly formed in a predetermined pitch alongeach of four sides. More specifically, in areas on one side and theother side in the X-axis direction of second water repellent plate 28 b(both sides in the horizontal direction in FIG. 4A), Y scales 39Y₁ and39Y₂ are formed respectively, and Y scales 39Y₁ and 39Y₂ are eachcomposed of a reflective grating (for example, a diffraction grating)having a periodic direction in the Y-axis direction in which grid lines38 having the longitudinal direction in the X-axis; direction are formedin a predetermined pitch along a direction parallel to the Y-axis (theY-axis direction).

Similarly, in areas on one side and the other side in the Y-axisdirection of second water repellent plate 28 b (both sides in thevertical direction in FIG. 4A), X scales 39X₁ and 39X₂ are formedrespectively in a state where the scales are placed between Y scales39Y₁ and 39Y₂, and X scales 39X₁ and 39X₂ are each composed of areflective grating (for example, a diffraction grating) having aperiodic direction in the X-axis direction in which grid lines 37 havingthe longitudinal direction in the Y-axis direction are formed in apredetermined pitch along a direction parallel to the X-axis (the X-axisdirection). As each of the scales, a scale is used that has a reflectivediffraction grating made by, for example, hologram or the like, on thesurface of the second water repellent plate 28 b. In this case, eachscale has grids made up of narrow slits, grooves or the like that aremarked at a predetermined distance (pitch) as graduations. The type ofdiffraction grating used for each scale is not limited, and not only thediffraction grating made up of grooves or the like that are mechanicallyformed, but also, for example, the diffraction grating that is createdby exposing an interference fringe on a photosensitive resin may beused. However, each scale is created by marking the graduations of thediffraction grating, for example, in a pitch between 138 nm to 4 μm, forexample, a pitch of 1 μm on a thin plate shaped glass. These scales arecovered with the liquid repellent film (water repellent film) describedabove. Incidentally, the pitch of the grating is shown much wider inFIG. 4A than the actual pitch, for the sake of convenience. The same istrue also in other drawings.

In this manner, in the embodiment, since the second water repellentplate 28 b itself constitutes the scales, a glass plate with low-thermalexpansion is to be used as the second water repellent plate 28 b.However, the present invention is not limited to this, and a scalemember made up of a glass plate or the like with low-thermal expansionon which a grating is formed may also be fixed on the upper surface ofwafer table WTB, for example, by a plate spring (or vacuum suction) orthe like so as to prevent local shrinkage/expansion. In this case, awater repellent plate to which the same water repellent coat is appliedon the entire surface may be used instead of plate 28. Or, wafer tableWTB may also be formed by materials with a low coefficient of thermalexpansion, and in such a case, a pair of Y scales and a pair of X scalesmay be directly formed on the upper surface of wafer table WTB.

Incidentally, in order to protect the diffraction grating, it is alsoeffective to cover the grating with a glass plate with low thermalexpansion that has water repellency (liquid repellency). In this case,as the glass plate, a plate whose thickness is the same level as thewafer, such as for example, a plate 1 mm thick, can be used, and theplate is set on the upper surface of wafer table WTB so that the surfaceof the glass plate becomes the same height (surface position) as thewafer surface.

Incidentally, a pattern for positioning is arranged for deciding therelative position between an encoder head and a scale near the edge ofeach scale (to be described later). The pattern for positioning isconfigured, for example, from grid lines that have differentreflectivity, and when the encoder head scans the pattern, the intensityof the output signal of the encoder changes. Therefore, a thresholdvalue is determined beforehand, and the position where the intensity ofthe output signal exceeds the threshold value is detected. Then, therelative position between the encoder head and the scale is set, withthe detected position as a reference.

Further, to the −Y edge surface and the −X edge surface of wafer tableWTB, mirror-polishing is applied, respectively, and as shown in FIG. 2,a reflection surface 17 a and a reflection surface 17 b are formed forinterferometer system 118 which will be described later in thedescription.

Measurement stage MST includes a stage main section 92 driven in the XYplane by a linear motor and the like (not shown), and a measurementtable MTB mounted on stage main section 92. Measurement stage MST isconfigured drivable in at least directions of three degrees of freedom(X, Y, and θz) with respect to base board 12 by a drive system (notshown).

Incidentally, the drive system of wafer stage WST and the drive systemof measurement stage MST are included in FIG. 6, and are shown as stagedrive system 124.

Various measurement members are arranged at measurement table MTB (andstage main section 92). As such measurement members, for example, asshown in FIGS. 2 and 52, members such as an uneven illuminance measuringsensor 94 that has a pinhole-shaped light-receiving section whichreceives illumination light IL on an image plane of projection opticalsystem PL, an aerial image measuring instrument 96 that measures anaerial image (projected image) of a pattern projected by projectionoptical system PL, a wavefront aberration measuring instrument 98 by theShack-Hartman method that is disclosed in, for example, the pamphlet ofInternational Publication No. 2003/065428 and the like are employed. Aswavefront aberration measuring instrument 98, the one disclosed in, forexample, the pamphlet of International Publication No. 99/60361 (thecorresponding EP Patent No. 1 079 223) can also be used.

As irregular illuminance sensor 94, the configuration similar to the onethat is disclosed in, for example, U.S. Pat. No. 4,465,368 and the likecan be used. Further, as aerial image measuring instrument 96, theconfiguration similar to the one that is disclosed in, for example, U.S.Patent Application Publication No. 2002/0041377 and the like can beused. Incidentally, in the embodiment, three measurement members (94, 96and 98) were to be arranged at measurement stage MST, however, the typeof the measurement member and/or the number is not limited to them. Asthe measurement members, for example, measurement members such as atransmittance measuring instrument that measures a transmittance ofprojection optical system PL, and/or a measuring instrument thatobserves local liquid immersion unit 8, for example, nozzle unit 32 (ortip lens 191) or the like may also be used. Furthermore, membersdifferent from the measurement members such as a cleaning member thatcleans nozzle unit 32, tip lens 191 or the like may also be mounted onmeasurement stage MST.

In the embodiment, as can be seen from FIG. 5A, the sensors that arefrequently used such as irregular illuminance sensor 94 and aerial imagemeasuring instrument 96 are placed on a centerline CL (Y-axis passingthrough the center) of measurement stage MST. Therefore, in theembodiment, measurement using these sensors can be performed by movingmeasurement stage MST only in the Y-axis direction without moving themeasurement stage in the X-axis direction.

In addition to each of the sensors described above, an illuminancemonitor that has a light-receiving section having a predetermined areasize that receives illumination light IL on the image plane ofprojection optical system PL may also be employed, which is disclosedin, for example, U.S. Patent Application Publication No. 2002/0061469and the like. The illuminance monitor is also preferably placed on thecenterline.

Incidentally, in the embodiment, liquid immersion exposure is performedin which wafer W is exposed with exposure light (illumination light) ILvia projection optical system PL and liquid (water) Lq, and accordinglyirregular illuminance sensor 94 (and the illuminance monitor), aerialimage measuring instrument 96 and wavefront aberration measuringinstrument 98 that are used in measurement using illumination light ILreceive illumination light IL via projection optical system PL andwater. Further, only part of each sensor such as the optical system maybe mounted on measurement table MTB (and stage main section 92), or theentire sensor may be placed on measurement table MTB (and stage mainsection 92).

Further, on the +Y edge surface and the −X edge surface of measurementtable MTB, reflection surfaces 19 a and 19 b are formed similar to wafertable WTB previously described (refer to FIGS. 2 and 5A).

As shown in FIG. 5B, a frame-shaped attachment member 42 is fixed to theend surface on the −Y side of stage main section 92 of measurement stageMST. Further, to the end surface on the −Y side of stage main section92, a pair of photodetection systems 44 are fixed in the vicinity of thecenter position in the X-axis direction inside an opening of attachmentmember 42, in the placement capable of facing a pair oflight-transmitting systems 36 described previously. Each ofphotodetection systems 44 is composed of an optical system such as arelay lens, a light receiving element such as a photo-multiplier tube,and a housing that houses them. As is obvious from FIGS. 4B and 5B andthe description so far, in the embodiment, in a state where wafer stageWST and measurement stage MST are closer together within a predetermineddistance in the Y-axis direction (including a contact state),illumination light IL that has been transmitted through each aerialimage measurement slit pattern SL of measurement plate 30 is guided byeach light-transmitting system 36 and received by the light-receivingelement of each photodetection system 44. That is, measurement plate 30,light-transmitting systems 36 and photodetection systems 44 constitutean aerial image measuring unit 45 (refer to FIG. 6), which is similar tothe one disclosed in, U.S. Patent Application Publication No.2002/0041377 referred to previously, and the like.

On attachment member 42, a fiducial bar (hereinafter, shortly referredto as an “FD bar”) which is made up of a bar-shaped member having arectangular sectional shape is arranged extending in the X-axisdirection. FD bar 46 is kinematically supported on measurement stage MSTby a full-kinematic mount structure.

Since FD bar 46 serves as a prototype standard (measurement standard),optical glass ceramics with a low coefficient of thermal expansion, suchas Zerodur (the brand name) of Schott AG are employed as the materials.The flatness degree of the upper surface (the surface) of FD bar 46 isset high to be around the same level as a so-called datum plane plate.Further, as shown in FIG. 5A, a reference grating (for example, adiffraction grating) 52 whose periodic direction is the Y-axis directionis respectively formed in the vicinity of the end portions on one sideand the other side in the longitudinal direction of FD bar 46. The pairof reference gratings 52 is formed placed apart from each other at apredetermined distance L, symmetric to the center in the X-axisdirection of FD bar 46, or more specifically, formed in a symmetricplacement to centerline CL previously described.

Further, on the upper surface of FD bar 46, a plurality of referencemarks M are formed in a placement as shown in FIG. 5A. The plurality ofreference marks M are formed in three-row arrays in the Y-axis directionin the same pitch, and the array of each row is formed being shiftedfrom each other by a predetermined distance in the X-axis direction. Aseach of reference marks M, a two-dimensional mark having a size that canbe detected by a primary alignment system and secondary alignmentsystems (to be described later) is used. Reference mark M may also bedifferent in shape (constitution) from fiducial mark FM, but in theembodiment, reference mark M and fiducial mark FM have the sameconstitution and also they have the same constitution with that of analignment mark of wafer W. Incidentally, in the embodiment, the surfaceof FD bar 46 and the surface of measurement table MTB (which may includethe measurement members described above) are also covered with a liquidrepellent film (water repellent film) severally.

In exposure apparatus 100 of the embodiment, although it is omitted inFIG. 1 from the viewpoint of avoiding intricacy of the drawing, aprimary alignment system AL1 having a detection center at a positionspaced apart from optical axis AX of projection optical system PL at apredetermined distance on the −Y side is actually placed on referenceaxis LV as shown in FIG. 3. Primary alignment system AL1 is fixed to thelower surface of a main frame (not shown) via a support member 54. Onone side and the other side in the X-axis direction with primaryalignment system AL1 in between, secondary alignment systems AL2 ₁ andAL2 ₂, and AL2 ₃ and AL2 ₄ whose detection centers are substantiallysymmetrically placed with respect to straight line LV are severallyarranged. That is, five alignment systems AL1 and AL2 ₁ to AL2 ₄ areplaced so that their detection centers are placed at different positionsin the X-axis direction, that is, placed along the X-axis direction.

As is representatively shown by secondary alignment system AL2 ₄, eachsecondary alignment system AL2 _(n) (n=1 to 4) is fixed to a tip(turning end) of an arm 56 _(n) (n=1 to 4) that can turn around arotation center O as the center in a predetermined angle range inclockwise and anticlockwise directions in FIG. 3. In the embodiment, apart of each secondary alignment system AL2 _(n) (for example, includingat least an optical system that irradiates an alignment light to adetection area and also leads the light that is generated from a subjectmark within the detection area to a light-receiving element) is fixed toarm 56 _(n) and the remaining section is arranged at the main frame thatholds projection unit PU. The X-positions of secondary alignment SystemsAL2 ₁, AL2 ₂, AL2 ₃ and AL2 ₄ are severally adjusted by rotating aroundrotation center O as the center. In other words, the detection areas (orthe detection centers) of secondary alignment systems AL2 ₁, AL2 ₂, AL2₃ and AL2 ₄ are independently movable in the X-axis direction.Accordingly, the relative positions of the detection areas of primaryalignment system AL1 and secondary alignment systems AL2 ₁, AL2 ₂, AL2 ₃and AL2 ₄ are adjustable in the X-axis direction. Incidentally, in theembodiment, the X-positions of secondary alignment systems AL2 ₁, AL2 ₂,AL2 ₃ and AL2 ₄ are to be adjusted by the rotation of the arms. However,the present invention is not limited to this, and a drive mechanism thatdrives secondary alignment systems AL2 ₁, AL2 ₂, AL2 ₃ and AL2 ₄ backand forth in the X-axis direction may also be arranged. Further, atleast one of secondary alignment systems AL2 ₁, AL2 ₂, AL2 ₃ and AL2 ₄can be moved not only in the X-axis direction but also in the Y-axisdirection. Incidentally, since part of each secondary alignment systemAL2 _(n) is moved by arm 56 _(n), positional information of the partthat is fixed to arm 56 _(n) is measurable by a sensor (not shown) suchas, for example, an interferometer or an encoder. The sensor may onlymeasure position information in the X-axis direction of secondaryalignment system AL2 _(n), or may also be capable of measuring positioninformation in another direction, for example, the Y-axis directionand/or the rotation direction (including at least one of the θx and θydirections).

On the upper surface of each arm 56 _(n), a vacuum pad 58 _(n) (n=1 to4, not shown in FIG. 3, refer to FIG. 6) that is composed of adifferential evacuation type air bearing is arranged. Further, arm 56_(n) can be turned by a rotation drive mechanism 60 _(n) (n−1 to 4, notshown in FIG. 3, refer to FIG. 6) that includes, for example, a motor orthe like, in response to instructions of main controller 20. Maincontroller 20 activates each vacuum pad 58 n to fix each arm 56 _(n) toa main frame (not shown) by suction after rotation adjustment of arm 56_(n). Thus, the state of each arm 56 _(n) after rotation angleadjustment, that is, a desired positional relation between primaryalignment system AL1 and four secondary alignment systems AL2 ₁ to AL2 ₄is maintained.

Incidentally, in the case a portion of the main frame facing arm 56 _(n)is a magnetic body, an electromagnet may also be employed instead ofvacuum pad 58.

In the embodiment, as each of primary alignment system AL1 and foursecondary alignment systems AL2 ₁ to AL2 ₄, for example, an FIA (Fieldimage Alignment) system by an image processing method is used thatirradiates a broadband detection beam that does not expose resist on awafer to a subject mark, and picks up an image of the subject markformed on a light-receiving plane by the reflected light from thesubject mark and an image of an index (an index pattern on an indexplate arranged within each alignment system) (not shown), using animaging device (such as CCD), and then outputs their imaging signals.The imaging signal from each of primary alignment system AL1 and foursecondary alignment systems AL2 ₁ to AL2 ₄ is supplied to maincontroller 20 in FIG. 6, via an alignment signal processing system (notshown).

Incidentally, each of the alignment systems described above is notlimited to the FIA system, and an alignment sensor, which irradiates acoherent detection light to a subject mark and detects a scattered lightor a diffracted light generated from the subject mark or makes twodiffracted lights (for example, diffracted lights of the same order ordiffracted lights being diffracted in the same direction) generated fromthe subject mark interfere and detects an interference light, cannaturally be used alone or in combination as needed. Further, in theembodiment, five alignment systems AL1 and AL2 ₁ to AL2 ₄ are to befixed to the lower surface of the main frame that holds projection unitPU, via support member 54 or arm 56 _(n). However, the present inventionis not limited to this, and for example, the five alignment systems mayalso be arranged on the measurement frame described earlier.

Next, a configuration and the like of interferometer system 118 (referto FIG. 6), which measures the positional information of wafer stage WSTand measurement stage MST, will be described.

The measurement principle of the interferometer will now be brieflydescribed, prior to describing a concrete configuration of theinterferometer system. The interferometer irradiates a measurement beam(measurement light) on a reflection surface set at a measurement object.The interferometer receives a synthesized light of the reflected lightand a reference beam, and measures the intensity of interference light,which is the reflected light (measurement light) and the reference beammade to interfere with each other, with their polarized directionsarranged. In this case, due to optical path difference ΔL of thereflected light and the reference beam, the relative phase (phasedifference) between the reflected light and the reference beam changesby KΔL. Accordingly, the intensity of the interference light changes inproportion to l+a·cos(KΔL). In this case, homodyne detection is to beemployed, and the wave number of the measurement light and the referencebeam is the same, expressed as K. Constant a is decided by the intensityratio of the measurement light and the reference beam. In this case, thereflection surface to the reference beam is arranged generally on theprojection unit PU side surface (in some cases, inside theinterferometer unit). The reflection surface of this reference beambecomes the reference position of the measurement. Accordingly, inoptical path difference ΔL, the distance from the reference position tothe reflection surface is reflected. Therefore, if the number of times(the number of fringes) of intensity change of the interference lightwith respect to the change of distance to the reflection surface ismeasured, displacement of the reflection surface provided in themeasurement object can be computed by the product of a counter value anda measurement unit. The measurement unit, in the case of aninterferometer of a single-pass method is half the wavelength of themeasurement light, and in the case of an interferometer of thedouble-pass method, one-fourth of the wavelength.

Now, in the case an interferometer of the heterodyne detection method isemployed, wave number K₁ of the measurement light and wave number K₂ ofthe reference beam are slightly different. In this case, when theoptical path length of the measurement light and the reference beam isL₁ and L₂, respectively, the phase difference between the measurementbeam and the reference beam is given KΔL+ΔKL₁, and the intensity of theinterference light changes in proportion to 1+a·cos(KΔL+ΔKL₁). However,optical path difference ΔL=L₁−L₂, ΔK=K₁−K₂, and K=K₂. When optical pathL₂ of the reference beam is sufficiently shorts and approximate ΔL≈L₁stands, the intensity of the interference light changes in proportion to1+a·cos [(K+ΔK) ΔL]. As it can be seen from above, the intensity of theinterference light periodically vibrates at a wavelength 2π/K of thereference beam along with the change of optical path difference ΔL, andthe envelope curve of the periodic vibration vibrates (beats) at a longcycle 2π/ΔK. Accordingly, in the heterodyne detection method, thechanging direction of optical path difference ΔL, or more specifically,the displacement direction of the measurement object can be learned fromthe long-period beat.

Incidentally, as a major cause of error of the interferometer, theeffect of temperature fluctuation (air fluctuation) of the atmosphere onthe beam optical path can be considered. Assume that wavelength λ of thelight changes to λ+Δλ by air fluctuation. Because the change of phasedifference KΔL by minimal change Δλ of the wavelength is wave numberK=2π/λ, 2πΔLΔλ/λ² can be obtained. In this case, when wavelength oflight λ=1 μm and minimal change Δλ=1 nm, the phase change becomes 2π×100with respect to an optical path difference ΔL=100 nm. This phase changecorresponds to displacement which is 100 times the measurement unit. Inthe case the optical path length which is set is long as is described,the interferometer is greatly affected by the air fluctuation whichoccurs in a short time, and is inferior in short-term stability. In sucha case, it is desirable to use a surface position measurement systemwhich will be described later that has an encoder or a Z head.

Interferometer system 118 includes a Y interferometer 16, Xinterferometers 126, 127, and 128, and Z interferometers 43A and 43B forposition measurement of wafer stage WST, and a Y interferometer 18 andan X interferometer 130 for position measurement of measurement stageMST, as shown in FIG. 2. By severally irradiating a measurement beam onreflection surface 17 a and reflection surface 17 b of wager table WTBand receiving a reflected light of each beam, Y interferometer 16 and Xinterferometers 126, 127, and 128 (X interferometers 126 to 128 are notshown in FIG. 1, refer to FIG. 2) measure a displacement of eachreflection surface from a reference position (for example, a fixedmirror is placed on the side surface of projection unit PU, and thesurface is used as a reference surface), or more specifically, measurethe positional information of wafer stage WST within the XY plane, andthe positional information that has been measured is supplied to maincontroller 20. In the embodiment, as it will be described later on, aseach interferometer a multiaxial interferometer that has a plurality ofmeasurement axes is used with an exception for a part of theinterferometers.

Meanwhile, to the side surface on the −Y side of stage main section 91,a movable mirror 41 having the longitudinal direction in the X-axisdirection is attached via a kinematic support mechanism (not shown), asshown in FIGS. 4A and 4B. Movable mirror 41 is made of a member which islike a rectangular solid member integrated with a pair of triangularprisms adhered to a surface (the surface on the −Y side) of therectangular solid member. As it can be seen from FIG. 2, movable mirror41 is designed so that the length in the X-axis direction is longer thanreflection surface 17 a of wafer table WTB by at least the spacingbetween the two Z interferometers which will be described later.

To the surface on the −Y side of movable mirror 41, mirror-polishing isapplied, and three reflection surfaces 41 b, 41 a, and 41 c are formed,as shown in FIG. 4B. Reflection surface 41 a configures a part of theedge surface on the −Y side of movable mirror 41, and reflection surface41 a is parallel with the XZ plane and also extends in the X-axisdirection. Reflection surface 41 b configures a surface adjacent toreflection surface 41 a on the +Z side, forming an obtuse angle toreflection surface 41 a, and spreading in the X-axis direction.Reflection surface 41 c configures a surface adjacent to the −Z side ofreflection surface 41 a, and is arranged symmetrically with reflectionsurface 41 b, with reflection surface 41 b in between.

A pair of z interferometers 43A and 43B (refer to FIGS. 1 and 2) thatirradiates measurement beams on movable mirror 41 is arranged facingmovable mirror 41.

As it can be seen when viewing FIGS. 1 and 2 together, Z interferometers43A and 43D are placed apart on one side and the other side of Yinterferometer 16 in the X-axis direction at a substantially equaldistance and at positions slightly lower than Y interferometer 16,respectively.

From each of the Z interferometers 43A and 43B, as shown in FIG. 1,measurement beam B1 along the Y-axis direction is irradiated towardreflection surface 41 b, and measurement beam B2 along the Y-axisdirection is irradiated toward reflection surface 41 c (refer to FIG.4B). In the embodiment, fixed mirror 47B having a reflection surfaceorthogonal to measurement beam B1 reflected off reflection surface 41 band a fixed mirror 47A having a reflection surface orthogonal tomeasurement beam B2 reflected off reflection surface 41 c are arranged,each extending in the X-axis direction at a position distanced apartfrom movable mirror 41 in the −Y-direction by a predetermined distancein a state where the fixed mirrors do not interfere with measurementbeams B1 and B2.

Fixed mirrors 47A and 47B are supported, for example, by the samesupport body (not shown) arranged in the frame (not shown) whichsupports projection unit PU.

Y interferometer 16, as shown in FIG. 2 (and FIG. 13), irradiatesmeasurement beams B4 ₁ and B4 ₂ on reflection surface 17 a of wafertable WTB along a measurement axis in the Y-axis direction spaced apartby an equal distance to the −X side and the +X side from reference axisIV previously described, and by receiving each reflected light, detectsthe position of wafer table WTB in the Y-axis direction (a Y position)at the irradiation point of measurement beams B4 ₁ and B4 ₂.Incidentally, in FIG. 1, measurement beams B4 ₁ and B4 ₂ arerepresentatively shown as measurement beam B4.

Further, Y interferometer 16 irradiates a measurement beam 53 towardreflection surface 41 a along a measurement axis in the Y-axis directionwith a predetermined distance in the Z-axis direction spaced betweenmeasurement beams B4 ₁ and B4 ₂, and by receiving measurement beam B3reflected off reflection surface 41 a, detects the Y position ofreflection surface 41 a (more specifically wafer stage WST) of movablemirror 41.

Main controller 20 computes the Y position (or to be more precise,displacement ΔY in the Y-axis direction) of reflection surface 17 a, ormore specifically, wafer table WTB (wafer stage WST), based on anaverage value of the measurement values of the measurement axescorresponding to measurement beams B4 ₁ and B4 ₂ of Y interferometer 16.Further, main controller 20 computes displacement (yawing amount)Δθz^((Y)) of wafer stage WST in the rotational direction around theZ-axis (the θz direction), based on a difference of the measurementvalues of the measurement axes corresponding to measurement beams B4 ₁and B4 ₂. Further, main controller 20 computes displacement (pitchingamount) Δθx in the θx direction of wafer stage WST, based on the Yposition (displacement ΔY in the Y-axis direction) of reflection surface17 a and reflection surface 41 a.

Further, as shown in FIGS. 2 and 13, X interferometer 126 irradiatesmeasurement beams B5 ₁ and B5 ₂ on wafer table WTB along the dualmeasurement axes spaced apart from a straight line (a reference axis) LHin the X-axis direction that passes the optical axis of projectionoptical system PL by the same distance. And, based on the measurementvalues of the measurement axes corresponding to measurement beams B5 ₁and B5 ₂, main controller 20 computes a position (an X position, or tobe more precise, displacement ΔX in the X-axis direction) of wafer stageWST in the X-axis direction. Further, main controller 20 computesdisplacement (yawing amount) Δθz^((X)) of wafer stage WST in the θzdirection from a difference of the measurement values of the measurementaxes corresponding to measurement beams B5 ₁ and B5 ₂. Incidentally,Δθz^((X)) obtained from X interferometer 126 and Δθz^((Y)) obtained fromY interferometer 16 are equal to each other, and represents displacement(yawing amount) Δθz of wafer stage WST in the θz direction.

Further, as shown in FIGS. 14 and 15, a measurement beam B7 from Xinterferometer 128 is irradiated on reflection surface 17 b of wafertable WTB along a straight line LUL, which is a line connecting anunloading position UP where unloading of the wafer on wafer table WTB isperformed and a loading position IP where loading of the wafer ontowafer table WTB is performed and is parallel to the X-axis. Further, asshown in FIGS. 16 and 17, a measurement beam B6 from X interferometer127 is irradiated on reflection surface 17 b of wafer table WTB along astraight line (a reference axis) LA, which passes through the detectioncenter of primary alignment system AL1 and is parallel to the X-axis.

Main controller 20 can obtain displacement ΔX of wafer stage WST in theX-axis direction from the measurement values of measurement beam B6 of Xinterferometer 127 and the measurement values of measurement beam 37 ofX interferometer 128. However, the placement of the three Xinterferometers 126, 127, and 128 is different in the Y-axis direction.Therefore, X interferometer 126 is used at the time of exposure as shownin FIG. 13, X interferometer 127 is used at the time of wafer alignmentas shown in FIG. 19, and X interferometer 128 is used at the time ofwafer loading shown in FIG. 15 and wafer unloading shown in FIG. 14.

From Z interferometers 43A and 43B previously described, measurementbeams B1 and B2 that proceed along the Y-axis are irradiated towardmovable mirror 41, respectively, as shown in FIG. 1. These measurementbeams B1 and B2 are incident on reflection surfaces 41 b and 41 c ofmovable mirror 41, respectively, at a predetermined angle of incidence(the angle is to be θ/2). Then, measurement beam 31 is sequentiallyreflected by reflection surfaces 41 b and 41 c, and then is incidentperpendicularly on the reflection surface of fixed mirror 47B, whereasmeasurement beam B2 is sequentially reflected by reflection surf aces 41c and 41 b and is incident perpendicularly on the reflection surface offixed mirror 47A. Then, measurement beams B2 and B1 reflected off thereflection surface of fixed mirrors 47A and 47B are sequentiallyreflected by reflection surfaces 41 b and 41 c again, or aresequentially reflected by reflection surfaces 41 c and 41 b again(returning the optical path at the time of incidence oppositely), andthen are received by Z interferometers 43A and 43B.

In this case, when displacement of movable mirror 41 (more specifically,wafer stage WST) in the Z-axis direction is ΔZo and displacement in theY-axis direction is ΔYo, an optical path length change ΔL1 ofmeasurement beam B1 and an optical path length change ΔL2 of measurementbeam B2 can respectively be expressed as in formulas (1) and (2) below.

ΔL1=ΔYoX(1+cos θ)+ΔZoX sin θ  (1)

ΔL2=ΔYoX(1+cos θ)−ΔZoX sin θ  (2)

Accordingly, from formulas (1) and (2), ΔZo and ΔYo can be obtainedusing the following formulas (3) and (4).

ΔZo=(ΔL1−ΔL2)/2 sin θ  (3)

ΔYo=(ΔL1+ΔL2)/{2/(1+cos θ)}  (4)

Displacements ΔZo and ΔYo above can be obtained with Z interferometers43A and 43B. Therefore, displacement which is obtained using Zinterferometer 43A is to be ΔZoR and ΔYoR, and displacement which isobtained using Z interferometer 43B is to be ΔZoL and ΔYoL. And thedistance between measurement beams B1 and B2 irradiated by Zinterferometers 43A and 43B, respectively, in the X-axis direction is tobe a distance D (refer to FIG. 2). Under such premises, displacement(yawing amount) Δθz of movable mirror 41 (more specifically, wafer stageWST) in the θz direction and displacement (rolling amount) Δθy in the θydirection can be obtained by the following formulas (5) and (6).

Δθz=tan⁻¹ {ΔYoR−ΔYoL)/D}  (5)

Δθy=tan⁻¹{(ΔZoL−ΔZoR)/D}  (6)

Accordingly, by using the formulas (3) to (6) above, main controller 20can compute displacement of wafer stage WST in four degrees of freedom,ΔZo, ΔYo, Δθz, and Δθy, based on the measurement results of Zinterferometers 43A and 43B.

In the manner described above, from the measurement results ofinterferometer system 118, main controller 20 can obtain displacement ofwafer stage WST in directions of six degrees of freedom (Z, X, Y, θz,θx, and θy directions).

Incidentally, in the embodiment, while a single stage which can bedriven in six degrees of freedom was employed as wafer stage WST,instead of this, wafer stage WST can be configured including a stagemain section 91, which is freely movable within the XY plane, and awafer table WTB, which is mounted on stage main section 91 and is finelydrivable relatively with respect to stage main section 91 in at leastthe Z-axis direction, the θx direction, and the θy direction, or a waferstage WST can be employed that has a so-called coarse and fine movementstructure where wafer table WTB can be configured finely movable in theX-axis direction, the Y-axis direction, and the θz direction withrespect to stage main section 91. However, in this case, a configurationin which positional information of wafer table WTB in directions of sixdegree of can be measured by interferometer system 118 will have to beemployed. Also for measurement stage MST, the stage can be configuredsimilarly, by a stage main section 92, and a measurement table MTB,which is mounted on stage main section 91 and has three degrees offreedom or six degrees of freedom. Further, instead of reflectionsurface 17 a and reflection surface 17 b, a movable mirror consisting ofa plane mirror can be arranged in wafer table WTB.

In the embodiment, however, position information within the XY plane(including the rotation information in the θz direction) for positioncontrol of wafer stage WST (wafer table WTB) is mainly measured by anencoder system (to be described later), and the measurement values ofinterferometers 16, 126, and 127 are secondarily used in cases such aswhen long-term fluctuation (for example, by temporal deformation or thelike of the scales) of the measurement values of the encoder system iscorrected (calibrated).

Incidentally, at least part of interferometer system 118 (such as anoptical system) may be arranged at the main frame that holds projectionunit PU, or may also be arranged integrally with projection unit PU thatis supported in a suspended state as is described above, however, in theembodiment, interferometer system 118 is to be arranged at themeasurement frame described above.

Incidentally, in the embodiment, positional information of wafer stageWST was to be measured with a reflection surface of a fixed mirrorarranged in projection unit PU serving as a reference surface, however,the position to place the reference surface at is not limited toprojection unit PU, and the fixed mirror does not always have to be usedto measure the positional information of wafer stage WST.

Further, in the embodiment, positional information of wafer stage WSTmeasured by interferometer system 118 is not used in the exposureoperation and the alignment operation which will be described later on,and was mainly to be used in calibration operations (more specifically,calibration of measurement values) of the encoder system, however, themeasurement information (more specifically, at least one of thepositional information in directions of six degrees of freedom) ofinterferometer system 118 can be used in the exposure operation and/orthe alignment operation. Further, using interferometer system 118 as abackup of an encoder system can also be considered, which will beexplained in detail later on. In the embodiment, the encoder systemmeasures positional information of wafer stage WST in directions ofthree degrees of freedom, or more specifically, the X-axis, the Y-axis,and the θz directions. Therefore, in the exposure operation and thelike, of the measurement information of interferometer system 118,positional information related to a direction that is different from themeasurement direction (the X-axis, the Y-axis, and the θz direction) ofwafer stage WST by the encoder system, such as, for example, positionalinformation related only to the θx direction and/or the θy direction canbe used, or in addition to the positional information in the differentdirection, positional information related to the same direction (morespecifically, at least one of the X-axis, the Y-axis, and the θzdirections) as the measurement direction of the encoder system can alsobe used. Further, in the exposure operation and the like, the positionalinformation of wafer stage WST in the Z-axis direction measured usinginterferometer system 118 can be used.

In addition, interferometer system 118 (refer to FIG. 6) includes a Yinterferometer 18 and an X interferometer 130 for measuring thetwo-dimensional position coordinates of measurement table MTB. Yinterferometer 18 and X interferometer 130 (X interferometer 130 is notshown in FIG. 1, refer to FIG. 2) irradiate measurement beams onreflection surfaces 19 a and 19 b of measurement table MTB as shown inFIG. 2, and measure the displacement from a reference position of eachreflection surface by receiving the respective reflected lights. Maincontroller 20 receives the measurement values of Y interferometer 18 andX interferometer 130, and computes the positional information (forexample, including at least the positional information in the X-axis andthe Y-axis directions and rotation information in the θz direction) ofmeasurement stage MST.

Incidentally, as the Y interferometer used for measuring measurementtable MTB, a multiaxial interferometer which is similar to Yinterferometer 16 used for measuring wafer stage WST can be used.Further, as the X interferometer used for measuring measurement tableMTB, a two-axis interferometer which is similar to X interferometer 126used for measuring wafer stage WST can be used. Further, in order tomeasure Z displacement, Y displacement, yawing amount, and rollingamount of measurement stage MST, interferometers similar to Zinterferometers 43A and 43B used for measuring wafer stage WST can beintroduced.

Next, the structure and the like of encoder system 150 (refer to FIG. 6)which measures positional information (including rotation information inthe θz direction) of wafer stage WST in the XY plane will be described.

In exposure apparatus 100 of the embodiment, as shown in FIG. 3, fourhead units 62A to 62D of encoder system 150 are placed in a state ofsurrounding nozzle unit 32 on all four sides. In actual, head units 62Ato 62D are fixed to the foregoing main frame that holds projection unitPU in a suspended state via a support member, although omitted in thedrawings such as FIG. 3 from the viewpoint of avoiding intricacy of thedrawings.

As shown in FIG. 37 head units 62A and 62C are placed on the +X side andthe −X side of projection unit PU, with the X-axis direction serving asa longitudinal direction. Head units 62A and 62C are each equipped witha plurality of (five, in this case) Y heads 65 _(i) and 64 _(j) (i,i=1-5) that are placed at a distance WD in the X-axis direction. Moreparticularly, head units 62A and 62C are each equipped with a pluralityof (four, in this case) Y heads (64 ₁ to 64 ₄ or 65 ₂ to 65 ₅) that areplaced on straight line (reference axis) LH which passes through opticalaxis AX of projection optical system PL and is also parallel to theX-axis at distance WD except for the periphery of projection unit PU,and a Y head (64 ₅ or 65 ₁) which is placed at a position apredetermined distance away in the −Y-direction from reference axis LHin the periphery of projection unit PU, or more specifically, on the −Yside of nozzle unit 32. Head units 62A and 62C are each also equippedwith five Z heads which will be described later on. Hereinafter, Y heads65 j and 64 i will also be described as Y heads 65 and 64, respectively,as necessary.

Head unit 62A constitutes a multiple-lens (five-lens, in this case) Ylinear encoder thereinafter appropriately shortened to “Y encoder” or“encoder”) 70A (refer to FIG. 6) that measures the position of waferstage WST (wafer table WTB) in the Y-axis direction (the Y-position)using Y scale 39Y₁ previously described. Similarly, head unit 62Cconstitutes a multiple-lens (five-lens, in this case) Y linear encoder70C (refer to FIG. 6) that measures the Y-position of wafer stage WSTusing Y scale 39Y₂ described above. In this case, distance WD in theX-axis direction of the five Y heads (64 _(i) or 65 _(j)) (morespecifically, measurement beams) that head units 62A and 62C are eachequipped with, is set slightly narrower than the width (to be moreprecise, the length of grid line 38) of Y scales 39Y₁ and 39Y₂ in theX-axis direction.

As shown in FIG. 3, head unit 62B is placed on the +Y side of nozzleunit 32 (projection unit PU), and is equipped with a plurality of, inthis case, four X heads 66 ₅ to 66 ₈ that are placed on reference axisLV previously described along Y-axis direction at distance WD. Further,head unit 62D is placed on the −Y side of primary alignment system AL1,on the opposite side of head unit 62B via nozzle unit 32 (projectionunit PU), and is equipped with a plurality of, in this case, four Xheads 66 ₁ to 66 ₄ that are placed on reference axis LV at distance WD.Hereinafter, X heads 66 ₁ to 66 ₈ will also be described as X head 66,as necessary.

Head unit 62B constitutes a multiple-lens (four-lens, in this case) Xlinear encoder (hereinafter, shortly referred to as an “X encoder” or an“encoder” as needed) 705 (refer to FIG. 6) that measures the position inthe x-axis direction (the X-position) of wafer stage WST using X scale39X₁ described above. Further, head unit 62D constitutes a multiple-lens(four-lens, in this case) X encoder 70D (refer to FIG. 6) that measuresthe X-position of wafer stage WST using X scale 39X₂ described above.

Here, the distance between adjacent X heads 66 (measurement beams) thatare equipped in each of head units 62B and 62D is set shorter than awidth in the Y-axis direction of X scales 39X₁ and 39X₂ (to be moreaccurate, the length of grid line 37). Further, the distance between Xhead 66 ₅ of head unit 62B farthest to the −Y side and X head 66 ₄ ofhead unit 62D farthest to the +Y side is set slightly narrower than thewidth of wafer stage WST in the Y-axis direction so that switching(linkage described below) becomes possible between the two X heads bythe movement of wafer stage WST in the Y-axis direction.

In the embodiment, furthermore, head units 62F and 62E are respectivelyarranged a predetermined distance away on the −Y side of head units 62Aand 62C. Although illustration of head units 62E and 62F is omitted inFIG. 3 and the like from the viewpoint of avoiding intricacy of thedrawings, in actual practice, head units 62E and 62F are fixed to theforegoing main frame that holds projection unit PU in a suspended statevia a support member. Incidentally, for example, in the case projectionunit PU is supported in a suspended state, head units 62E and 62F, andhead units 62A to 62D which are previously described can be supported ina suspended state integrally with projection unit PU, or can be arrangedat the measurement frame described above.

Head unit 62E is equipped with four Y heads 67 ₁ to 67 ₄ whose positionsin the X-axis direction are different. More particularly, head unit 62Eis equipped with three Y heads 67 ₁ to 67 ₃ placed on the −X side of thesecondary alignment system AL2 ₁ on reference axis LA previouslydescribed at substantially the same distance as distance WD previouslydescribed, and one Y head 67 ₄ which is placed at a position apredetermined distance (a distance slightly shorter than WD) away on the+X side from the innermost (the +X side) Y head 67 ₃ and is also on the+Y side of the secondary alignment system AL2 ₁ a predetermined distanceaway to the +Y side of reference axis LA.

Head unit 62F is symmetrical to head unit 62E with respect to referenceaxis LV, and is equipped with four Y heads 68 ₁ to 68 ₄ which are placedin symmetry to four Y heads 67 ₁ to 67 ₄ with respect to reference axisLV. Hereinafter, Y heads 67 ₁ to 67 ₄ and 68 ₁ to 68 ₄ will also bedescribed as Y heads 67 and 68, respectively, as necessary. In the caseof an alignment operation and the like which will be described later on,at least one each of Y heads 67 and 68 faces Y scale 39Y₂ and 39Y₁,respectively, and by such Y heads 67 and 68 (more specifically, Yencoders 70E and 70F which are configured by these Y heads 67 and 68),the Y position (and the θz rotation) of wafer stage WST is measured.

Further, in the embodiment, at the time of baseline measurement (Sec-BHK(interval)) and the like of the secondary alignment system AL21 whichwill be described later on, Y head 67 ₃ and 68 ₂ which are adjacent tothe secondary alignment systems AL2 ₁ and AL2 ₄ in the X-axis directionf ace the pair of reference gratings 52 of FD bar 46, respectively, andby Y heads 67 ₃ and 68 ₂ that face the pair of reference gratings 52,the Y position of FD bar 46 is measured at the position of eachreference grating 52. In the description below, the encoders configuredby Y heads 67 ₃ and 68 ₂ which face the pair of reference gratings 52,respectively, are referred to as Y linear encoders (also shortlyreferred to as a “Y encoder” or an “encoder” as needed) 70E₂ and 70F₂.Further, for identification, Y encoders 70 and 70 configured by Y heads67 and 68 that face Y scales 39Y₂ and 39Y₁ described above,respectively, will be referred to as Y encoders 70E₁ and 70F₁.

The linear encoders 70A to 70F described above measure the positioncoordinates of wafer stage WST at a resolution of, for example, around0.1 nm, and the measurement values are supplied to main controller 20.Main controller 20 controls the position within the XY plane of waferstage WST based on three measurement values of linear encoders 70A to70D or on three measurement values of encoders 70B, 70D, 70E₁, and 70F₁,and also controls the rotation in the θz direction of FD bar 46 based onthe measurement values of linear encoders 70E₂ and 70F₂.

In exposure apparatus 100 of the embodiment, as shown in FIG. 3, amultipoint focal position detecting system (hereinafter, shortlyreferred to as a “multipoint AF system”) by an oblique incident methodis arranged, which is composed of an irradiation system 90 a and aphotodetection system 90 b, having a configuration similar to the onedisclosed in, for example, U.S. Pat. No. 5,448,332 and the like. In theembodiment, as an example, irradiation system 90 a is placed on the +Yside of the −X end portion of head unit 62E previously described, andphotodetection system 90 b is placed on the +Y side of the +X endportion of head unit 62F previously described in a state opposingirradiation system 90 a.

A plurality of detection points of the multipoint AF system (90 a, 90 b)are placed at a predetermined distance along the X-axis direction on thesurface to be detected. In the embodiment, the plurality of detectionpoints are placed, for example, in the arrangement of a matrix havingone row and M columns (M is a total number of detection points) orhaving two rows and N columns (N is a half of a total number ofdetection points). In FIG. 3, the plurality of detection points to whicha detection beam is severally irradiated are not individually shown, butare shown as an elongate detection area (beam area) AF that extends inthe X-axis direction between irradiation system 90 a and photodetectionsystem 90 b. Because the length of detection area AF in the X-axisdirection is set to around the same as the diameter of wafer W, by onlyscanning wafer W in the Y-axis direction once, position information(surface position information) in the Z-axis direction across the entiresurface of wafer W can be measured. Further, since detection area AF isplaced between liquid immersion area 14 (exposure area IA) and thedetection areas of the alignment systems (AL1, AL2 ₁ to AL2 ₄) in theY-axis direction, the detection operations of the multipoint AF systemand the alignment systems can be performed in parallel. The multipointAF system may also be arranged on the main frame that holds projectionunit PU or the like, however, in the embodiment, the system will bearranged on the measurement frame previously described.

Incidentally, the plurality of detection points are to be placed in onerow and M columns, or two rows and N columns, but the number(s) of rowsand/or columns is/are not limited to these numbers. However, in the casethe number of tows is two or more, the positions in the X-axis directionof detection points are preferably made to be different between thedifferent rows. Moreover, the plurality of detection points is to beplaced along the X-axis direction. However, the present invention is notlimited to this and all of or some of the plurality of detection pointsmay also be placed at different positions in the Y-axis direction. Forexample, the plurality of detection points may also be placed along adirection that intersects both of the X-axis and the Y-axis. That is,the positions of the plurality of detection points only have to bedifferent at least in the X-axis direction. Further, a detection beam isto be irradiated to the plurality of detection points in the embodiment,but a detection beam may also be irradiated to, for example, the entirearea of detection area AF. Furthermore, the length of detection area AFin the X-axis direction does not have to be nearly the same as thediameter of wafer W.

In the vicinity of detection points located at both ends out of aplurality of detection points of the multipoint AF system (90 a, 90 b),that is, in the vicinity of both end portions of beam area AF, heads 72a and 72 b, and 72 c and 72 d of surface position sensors for Z positionmeasurement (hereinafter, shortly referred to as “Z heads”) are arrangedeach in a pair, in symmetrical placement with respect to reference axisLV. Z heads 72 a to 72 d are fixed to the lower surface of a main frame(not shown). Incidentally, Z heads 72 a to 72 d may also be arranged onthe measurement frame described above or the like.

As Z heads 72 a to 72 d, a sensor head that irradiates a light to wafertable WTB from above, receives the reflected light and measures positioninformation of the water table WTB surface in the Z-axis directionorthogonal to the XY plane at the irradiation point of the light, as anexample, a head of an optical displacement sensor (a sensor head by anoptical pickup method), which has a configuration like an optical pickupused in a CD drive device, is used.

Furthermore, head units 62A and 62C previously described arerespectively equipped with Z heads 76 _(j) and 74 _(i) (i, j=1-5), whichare five heads each, at the same X position as Y heads 65 _(j) and 64_(i) (i, j=1-5) that head units 62A and 62C are respectively equippedwith, with the Y position shifted. In this case, Z heads 76 ₃ to 76 ₅and 74 ₁ to 74 ₃, which are three heads each on the outer side belongingto head units 62A and 62C, respectively, are placed parallel toreference axis LH a predetermined distance away in the +Y direction fromreference axis LH. Further, Z heads 76 ₁ and 74 ₅, which are heads onthe innermost side belonging to head units 62A and 62C, respectively,are placed on the +Y side of projection unit PU, and Z heads 76 ₂ and 74₄, which are the second innermost heads, are placed on the −Y side of Yheads 65 ₂ and 64 ₄, respectively. And Z heads 76 _(j), 74 _(i) (i,j=1-5), which are five heads each belonging to head unit 62A and 62C,respectively, are placed symmetric to each other with respect toreference axis LV. Incidentally, as each of the Z heads 76 and 74, anoptical displacement sensor head similar to Z heads 72 a to 72 ddescribed above is employed. Incidentally, the configuration and thelike of the Z heads will be described later on.

In this case, Z head 74; is on a straight line parallel to the Y-axis,the same as is with Z heads 72 a and 72 b previously described.Similarly, Z head 76 ₃ is on a straight line parallel to the Y-axis, thesame as is with Z heads 72 c and 72 d previously described.

Z heads 72 a to 72 d, Z heads 74 ₁ to 74 ₅, and Z heads 76 ₁ to 76 ₅described above connect to main controller 20 via a signalprocessing/selection device 170, as shown in FIG. 6. Main controller 20selects an arbitrary Z head from Z heads 72 a to 72 d, Z heads 74 ₁ to74 ₅, and Z heads 76 _(i) to 76 ₅ via signal processing/selection device170 and makes the head move into an operating state, and then receivesthe surface position information detected by the Z head which is in theoperating state via signal processing/selection device 170. In theembodiment, a surface position measurement system 180 (a part ofmeasurement system 200) that measures positional information of waferstage WST in the Z-axis direction and the direction of inclination withrespect to the XY plane is configured, including Z heads 72 a to 72 d, Zheads 74 ₁ to 74 ₅, and Z heads 76 ₁ to 76 ₅, and signalprocessing/selection device 170.

Incidentally, in FIG. 3, measurement stage MST is omitted and a liquidimmersion area that is formed by water Lq held in the space betweenmeasurement stage MST and tip lens 191 is shown by a reference code 14.Further, in FIG. 3, a reference code UP indicates an unloading positionwhere a wafer on wafer table WTB is unloaded, and a reference code LPindicates a loading position where a wafer is loaded on wafer table WTB.In the embodiment, unloading position UP and loading position LP are setsymmetrically with respect to reference axis LV. Incidentally, unloadingposition UP and loading position LP may be the same position.

FIG. 6 shows the main configuration of the control system of exposureapparatus 100. The control system is mainly configured of maincontroller 20 composed of a microcomputer (or workstation) that performsoverall control of the entire apparatus. In memory 34 which is anexternal memory connected to main controller 20, correction informationis stored of measurement instrument systems such as interferometersystem 118, encoder system 150 (encoders 70A to 70F), Z heads 72 a to 72d, 74 ₁ to 74 ₅, 76 ₁ to 76 ₅ and the like. Incidentally, in FIG. 6,various sensors such as irregular illuminance sensor 94, aerial imagemeasuring instrument 96 and wavefront aberration measuring instrument 98that are arranged at measurement stage MST are collectively shown as asensor group 99.

Next, the configuration and the like of Z heads 72 a to 72 d, 74 ₁ to 74₅, and 76 ₁ to 76 ₅ will be described, focusing on Z head 72 a shown inFIG. 7 as a representative.

As shown in FIG. 7, Z head 72 a is equipped with a focus sensor FS, asensor main section ZH which houses focus sensor FS, a drive section(not shown) which drives sensor main section ZH in the Z-axis direction,a measurement section ZE which measures displacement of sensor mainsection ZH in the Z-axis direction and the like.

As focus sensor FS, an optical displacement sensor similar to an opticalpickup used in a CD drive unit that irradiates a probe beam LB on ameasurement target surface S and optically reads the displacement ofmeasurement surface S by receiving the reflected light is used. Theconfiguration and the like of the focus sensor will be described laterin the description. The output signal of focus sensor FS is sent to thedrive section (not shown).

The drive section (not shown) includes an actuator such as, for example,a voice coil motor, and one of a mover and a stator of the voice coilmotor is fixed to sensor main section ZH, and the other is fixed to apart of a housing (not shown) which houses the sensor main section ZH,measurement section ZE and the like, respectively. The drive sectiondrives sensor main section ZH in the Z-axis direction according to theoutput signals from focus sensor FS so that the distance between sensormain section ZH and measurement target surface S is constantlymaintained (or to be more precise, so that measurement target surface Sis maintained at the best focus position of the optical system of focussensor FS). By this drive, sensor main section ZH follows thedisplacement of measurement target surface S in the Z-axis direction,and a focus lock state is maintained.

As measurement section ZE, in the embodiment, an encoder by thediffraction interference method is used as an example. Measurementsection ZE includes a reflective diffraction grating EG whose periodicdirection is the Z-axis direction arranged on a side surface of asupport member SM fixed on the upper surface of sensor main section ZHextending in the Z-axis direction, and an encoder head EH which isattached to the housing (not shown) facing diffraction grating EG.Encoder head ER reads the displacement of sensor main section ZH in theZ-axis direction by irradiating probe beam EL on diffraction grating EG,receiving the reflection/diffraction light from diffraction grating EGwith a light-receiving element, and reading the deviation of anirradiation point of probe beam EL from a reference point (for example,the origin).

In the embodiment, in the focus lock state, sensor main section ZH isdisplaced in the Z-axis direction so as to constantly maintain thedistance with measurement target surface S as described above.Accordingly, by encoder head EH of measurement section ZE measuring thedisplacement of sensor main section ZH in the Z-axis direction, surfaceposition (z position) of measurement target surface S is measured.Measurement values of encoder head ER is supplied to main controller 20via signal processing/selection device 170 previously described asmeasurement values of Z head 72 a.

As shown in FIG. 8A, as an example, focus sensor FS includes threesections, an irradiation system FS₁, an optical system FS₂, and aphotodetection system FS₃.

Irradiation system FS₁ includes, for example, a light source LD made upof laser diodes, and a diffraction grating plate (a diffractive opticalelement) ZG placed on the optical path of a laser beam outgoing fromlight source LD.

Optical system FS₂ includes, for instance, a diffraction light of thelaser beam generated in diffraction grating plate ZG, or morespecifically, a polarization beam splitter PBS, a collimator lens CL, aquarter-wave plate (a λ/4 plate) WP, and object lens OL and the likeplaced sequentially on the optical path of probe beam LB₁.

Photodetection system FS₃, for instance, includes a cylindrical lens CYLand a tetrameric light receiving element ZD placed sequentially on areturn optical path of reflected beam LB₂ of probe beam LB₁ onmeasurement target surface S.

According to focus sensor FS, the linearly polarized laser beamgenerated in light source LD of irradiation system FS₁ is irradiated ondiffraction grating plate ZG, and diffraction light (probe beam) LB₁ isgenerated in diffraction grating plate ZG. The central axis (principalray) of probe beam LB₁ is parallel to the Z-axis and is also orthogonalto measurement target surface S.

Then, probe beam LB₁, or more specifically, light having a polarizationcomponent that is a P-polarized light with respect to a separation planeof polarization beam splitter PBS, is incident on optical system FS₂. Inoptical system FS₂, probe beam LB₁ passes through polarization beamsplitter PBS and is converted into a parallel beam at collimator lensCL, and then passes through λ/4 plate WP and becomes a circularpolarized light, which is condensed at object lens OL and is irradiatedon measurement target surface S. Accordingly, at measurement targetsurface S, reflected light (reflected beam) LB₂ occurs, which is acircular polarized light that proceeds inversely to the incoming lightof probe beam LB₁. Then, reflected beam LB₂ traces the optical path ofthe incoming light (probe beam LB₁) the other way around, and passesthrough object lens OL, λ/4 plate WP, collimator lens CL, and thenproceeds toward polarization beam splitter PBS. In this case, becausethe beam passes through λ/4 plate WP twice, reflected beam LB₂ isconverted into an S-polarized light. Therefore, the proceeding directionof reflected beam LB₂ is bent at the separation plane of polarizationbeam splitter PBS, so that it moves toward photodetection system FS₃.

In photodetection system FS₃, reflected beam LB₂ passes throughcylindrical lenses CYL and is irradiated on a detection surface oftetrameric light receiving element ZD. In this case, cylindrical lensesCYL is a “cambered type” lens, and as shown in FIG. 8B, the YZ sectionhas a convexed shape with the convexed section pointing the Y-axisdirection, and as shown also in FIG. 8C, the XY section has arectangular shape. Therefore, the sectional shape of reflected beam LB₂which passes through cylindrical lenses CYL is narrowed asymmetricallyin the Z-axis direction and the X-axis direction, which causesastigmatism.

Tetrameric light receiving element ZD receives reflected beam LB₂ on itsdetection surface. The detection surface of tetrameric light receivingelement ZD has a square shape as a whole as shown in FIG. 9A, and it isdivided equally into four detection areas a, b, c, and d with the twodiagonal lines serving as a separation line. The center of the detectionsurface will be referred to as O_(ZD).

In this case, in an ideal focus state (a state in focus) shown in FIG.8A, or more specifically, in a state where probe beam LB₁ is focused onmeasurement target surface S₀, the cross-sectional shape of reflectedbeam LB₂ on the detection surface becomes a circle with center O_(ZD)serving as a center, as shown in view 9C.

Further, in the so-called front-focused state (more specifically, astate equivalent to a state where measurement target surface S is atideal position S₀ and tetrameric light receiving element ZD is at aposition shown by reference code 1 in FIGS. 8B and 8C) where probe beamLB₁ focuses on measurement target surface S₁ in FIG. 8A, thecross-sectional shape of reflected beam LB₂ on the detection surfacebecomes a horizontally elongated circle with center O_(ZD) serving as acenter as shown in FIG. 9B.

Further, in the so-called back-focused state (more specifically, a stateequivalent to a state where measurement target surface S is at idealposition S₀ and tetrameric light receiving element ZD is at a positionshown by reference code—1 in FIGS. 8B and 8C) where probe beam LB₁focuses on measurement target surface S⁻¹ in FIG. BA, thecross-sectional shape of reflected beam LB₂ on the detection surfacebecomes a longitudinally elongated circle with center O_(ZD) serving asa center as shown in FIG. 9D.

In an operational circuit (not shown) connected to tetrameric lightreceiving element ZD, a focus error I expressed as in the followingformula (7) is computed and output to the drive section (not shown),with the intensity of light received in the four detection areas a, b,c, and d expressed as Ia, Ib, Ic, and Id, respectively.

I=(Ia+Ic)−(Ib+Id)  (7)

Incidentally, in the ideal focus state described above, because the areaof the beam cross-section in each of the four detection areas is equalto each other, focus error I=0 can be obtained. Further, in the frontfocused state described above, according to formula (7), focus errorbecomes I<0, and in the back focused state, according to formula (7),focus error becomes I>0.

The drive section (not shown) receives focus error I from a detectionsection FS₃ within focus sensor FS, and drives sensor main body ZH whichstored focus sensor FS in the Z-axis direction so as to reproduce I=0.By this operation of the drive section, because sensor main section ZHis also displaced following measurement target surface S, the probe beamfocuses on measurement target surface S without fail, or morespecifically, the distance between sensor main section ZH andmeasurement target surface S is always constantly maintained (focus lockstate is maintained).

Meanwhile, the drive section (not shown) can also drive and positionsensor main section ZH in the Z-axis direction so that a measurementresult of measurement section ZE coincides with an input signal from theoutside of Z head 72 a. Accordingly, the focus of probe beam LB can alsobe positioned at a position different from the actual surface positionof measurement target surface S. By this operation (scale servo control)of the drive section, processes such as return process in the switchingof the Z heads, avoidance process at the time of abnormality generationin the output signals and the like can be performed.

In the embodiment, as is previously described, an encoder is adopted asmeasurement section ZE, and encoder head ER is used to read the Zdisplacement of diffraction grating EG set in sensor main section ZH.Because encoder head ER is a relative position sensor which measures thedisplacement of the measurement object (diffraction grating EG) from areference point, it is necessary to determine the reference point. Inthe embodiment, the reference position (for example, the origin) of theZ displacement can be determined by detecting an edge section ofdiffraction grating EG, or in the case a lay out pattern is arranged indiffraction grating EG, by detecting the pattern for positioning. In anycase, reference surface position of measurement target surface S can bedetermined in correspondence with the reference position of diffractiongrating EG, and the Z displacement of measurement target surface S fromthe reference surface position, or more specifically, the position inthe Z-axis direction can be measured. Incidentally, at the start up andthe restoration of the Z head, setting of the reference position (forexample, the origin, or more specifically, the reference surfaceposition of measurement target surface S) of diffraction grating EG isexecuted without fail. In this case, it is desirable for the referenceposition to be set around the center of the movement range of sensormain section ZH. Therefore, a drive coil for adjusting the focalposition of the optical system can be arranged to adjust the Z positionof object lens OL so that the reference surface position correspondingto the reference position around the center coincides with the focalposition of the optical system in the focus sensor FS.

In Z head 72 a, because sensor main section ZH and measurement sectionZE are housed together inside the housing (not shown) and the part ofthe optical path length of probe beam LB₁ which is exposed outside thehousing is extremely short, the influence of air fluctuation isextremely small. Accordingly, even when compared, for example, with alaser interferometer, the sensor including the Z head is much moresuperior in measurement stability (short-term stability) during a periodas short as while the air fluctuates.

The other Z heads are also configured and function in a similar manneras Z head 72 a described above. As is described, in the embodiment, aseach Z head, a configuration is employed where the diffraction gratingsurfaces of Y scales 39Y₁, 39Y₂ and the like are observed from above(the +Z direction) as in the encoder. Accordingly, by measuring thesurface position information of the upper surface of wafer table WTB atdifferent positions with the plurality of Z heads, the position of waferstage WST in the Z-axis direction, the θy rotation (rolling), and the θxrotation (pitching) can be measured. However, in the embodiment, becausethe accuracy of pitching control of wafer stage WST is not especiallyimportant on exposure, the surface position measurement system includingthe Z head does not measure pitching, and a configuration was employedwhere one Z head each races Y scales 39Y₁ and 39Y₂.

Next, detection of position information (surface position information)of the wafer W surface in the Z-axis direction (hereinafter, referred toas focus mapping) that is performed in exposure apparatus 100 of theembodiment will be described.

On the focus mapping, as is shown in FIG. 10A, main controller 20controls the position within the XY plane of wafer stage WST based on Xhead 66 ₃ facing X scale 39X₂ (X linear encoder 70D) and two Y heads 68₂ and 67 ₃ facing Y scales 39Y₁ and 39Y₂ respectively (Y linear encoders70F1 and 70E1). In the state of FIG. 10A, a straight line (centerline)parallel to the Y-axis that passes through the center of wafer table WTB(which substantially coincides with the center of water W) coincideswith reference axis LV previously described. Further, although it isomitted in the drawing here, measurement stage MST is located on the +Yside of water stage WST, and water is retained in the space between FDbar 46, wafer table WTB and tip lens 191 of projection optical system PLpreviously described (refer to FIG. 18).

Then, in this state, main controller 20 starts scanning of wafer stageWST in the +Y direction, and after having started the scanning,activates (turns ON) both Z heads 72 a to 72 d and the multipoint AFsystem (90 a, 90 b) by the time when wafer stage WST moves in the +Ydirection and detection beams (detection area AF) of the multipoint AFsystem (90 a, 90 b) begin to be irradiated on wafer W.

Then, in a state where Z heads 72 a to 72 d and the multipoint AF system(90 a, 90 b) simultaneously operate, as is shown in FIG. 10B, positioninformation (surface position information) of the wafer table WTBsurface (surface of plate 28) in the Z-axis direction that is measuredby Z heads 72 a to 72 d and position information (surface positioninformation) of the wafer W surface in the Z-axis direction at aplurality of detection points that is detected by the multipoint AFsystem (90 a, 90 b) are loaded at a predetermined sampling intervalwhile wafer stage WST is proceeding in the +Y direction, and three kindsof information, which are the two kinds of surface position informationthat has been loaded and the measurement values of Y linear encoders F₁and 70E₁ at the time of each sampling, are made to correspond to oneanother, and then are sequentially stored in memory (not shown) (or inmemory 34).

Then, when the detection beams of the multipoint AF system (90 a, 90 b)begin to miss wafer W, main controller 20 ends the sampling describedabove and converts the surface position information at each detectionpoint of the multipoint AF system (90 a, 90 b) into data which uses thesurface position information by Z heads 72 a to 72 d that has beenloaded simultaneously as a reference.

More specifically, based on an average value of the measurement valuesof Z heads 72 a and 72 b, surface position information at apredetermined point (for example, corresponding to a midpoint of therespective measurement points of Z heads 72 a and 72 b, that is, a pointon substantially the same X-axis as the array of a plurality ofdetection points of the multipoint AF system (90 a, 90 b): hereinafter,this point is referred to as a left measurement point P1) on an area (anarea where Y scale 39Y₂ is formed) near the edge section on the −X sideof plate 28 is obtained. Further, based on an average value of themeasurement values of Z heads 72 c and 72 d, surface positioninformation at a predetermined point (for example, corresponding to amidpoint of the respective measurement points of Z heads 72 c and 72 d,that is, a point on substantially the same X-axis as the array of aplurality of detection points of the multipoint AF system (90 a, 90 b):hereinafter, this point is referred to as a right measurement point P2)on an area (an area where Y scale 39Y₁ is formed) near the edge sectionon the +X side of plate 28 is obtained. Then, as shown in FIG. 10C, maincontroller 20 converts the surface position information at eachdetection point of the multipoint AF system (90 a, 90 b) into surfaceposition data z1-zk, which uses a straight line that connects thesurface position of left measurement point P1 and the surface positionof right measurement point P2 as a reference. Main controller 20performs such a conversion on all information taken in during thesampling.

By obtaining such converted data in advance in the manner describedabove, for example, in the case of exposure, main controller 20 measuresthe wafer table WTB surface (a point on the area where Y scale 39Y₂ isformed (a point near left measurement point P1 described above) and apoint on the area where Y scale 39Y₁ is formed (a point near rightmeasurement point P1 described above)) with Z heads 74 _(i) and 76 _(j)previously described, and computes the z position and θy rotation(rolling) amount θy of wafer stage WST. Then, by performing apredetermined operation using the Z position, the rolling amount θy, andthe θx rotation (pitching) amount θx of wafer stage WST measured with Yinterferometer 16, and computing the Z position (Z₀), rolling amount θy,and pitching amount θx of the wafer table WTB surface in the center (theexposure center) of exposure area IA previously described, and thenobtaining the straight line passing through the exposure center thatconnects the surface position of left measurement point P1 and thesurface position of right measurement point P2 described above based onthe computation results, it becomes possible to perform the surfaceposition control (focus leveling control) of the upper surface of waferW without actually acquiring the surface position information of thewafer W surface by using such straight line and surface position dataz1-zk. Accordingly, because there is no problem even if the multipointAF system is placed at a position away from projection optical systemPL, the focus mapping of the embodiment can suitably be applied also toan exposure apparatus and the like that has a short working distance.

Incidentally, in the description above, while the surface position ofleft measurement point P1 and the surface position of right measurementpoint P2 were computed based on the average value of the measurementvalues of Z heads 72 a and 72 b, and the average value of Z heads 72 cand 72 d, respectively, the surface position information at eachdetection point of the multipoint AF system (90 a, 90 b) can also beconverted, for example, into surface position data which uses thestraight line connecting the surface positions measured by Z heads 72 aand 72 c as a reference. In this case, the difference between themeasurement value of Z head 72 a and the measurement value of Z head 72b obtained at each sampling timing, and the difference between themeasurement value of Z head 72 c and the measurement value of Z head 72a obtained at each sampling timing are to be obtained severally inadvance. Then, when performing surface position control at the time ofexposure or the like, by measuring the wafer table WTB surface with Zheads 74 _(i) and 76 _(j) and computing the Z-position and the θyrotation of wafer stage WST, and then performing a predeterminedoperation using these computed values, pitching amount θx of wafer stageWST measured by Y interferometer 16, surface position data z1 to zkpreviously described, and the differences described above, it becomespossible to perform surface position control of wafer W, withoutactually obtaining the surface position information of the wafersurface.

However, the description so far is made, assuming that unevenness doesnot exist on the wafer table WTB surface in the X-axis direction.Accordingly, hereinafter, to simplify the description, unevenness is notto exist on the wafer table WTB surface in the X-axis direction and theY-axis direction.

Next, focus calibration will be described. Focus calibration refers to aprocess where a processing of obtaining a relation between surfaceposition information of wafer table WTB at end portions on one side andthe other side in the X-axis direction in a reference state anddetection results (surface position information) at representativedetection points on the measurement plate 30 surface of multipoint AFsystem (90 a, 90 b) (former processing of focus calibration), and aprocessing of obtaining surface position information of wafer table WTBat end portions on one side and the other side in the X-axis directionthat correspond to the best focus position of projection optical systemPL detected using aerial image measurement device 45 in a state similarto the reference state above (latter processing of focus calibration)are performed, and based on these processing results, an offset ofmultipoint AF system (90 a, 90 b) at representative detection points, orin other words, a deviation between the best focus position ofprojection optical system PL and the detection origin of the multipointAF system, is obtained.

On the focus calibration, as is shown in FIG. 11A, main controller 20controls the position within the XY plane of wafer stage WST based on Xhead 66 ₂ facing X scale 39X₂ (X linear encoder 70D) and two Y heads 68₂ and 67 ₃ facing Y scales 39Y₁ and 39Y₂ respectively (Y linear encoders70A and 70C). The state of FIG. 11A is substantially the same as thestate in 10A previously described. However, in the state of FIG. 11A,wafer stage WST is at a position where a detection beam from multipointAF system (90 a, 90 b) is irradiated on measurement plate 30 previouslydescribed in the Y-axis direction.

(a) In this state, main controller 20 performs the former processing offocus calibration as in the following description. More specifically,while detecting surface position information of the end portions on oneside and the other side of wafer table WTB in the X-axis direction thatis detected by Z heads 72 a, 72 b, 72 c and 72 d previously described,main controller 20 uses the surface position information as a reference,and detects surface position information of the measurement plate 30(refer to FIG. 3) surface previously described using the multipoint AFsystem (90 a, 90 b). Thus, a relation between the measurement values ofZ heads 72 a, 72 b, 72 c and 72 d (surface position information at endportions on one side and the other side of wafer table WTB in the X-axisdirection) and the detection results (surface position information) at adetection point (the detection point located in the center or thevicinity thereof out of a plurality of detection points) on themeasurement plate 30 surface of the multipoint AF system (90 a, 90 b),in a state where the centerline of wafer table WTB coincides withreference line LV, is obtained.(b) Next, main controller 20 moves wafer stage WST in the +Y directionby a predetermined distance, and stops wafer stage WST at a positionwhere measurement plate 30 is located directly below projection opticalsystem PL. Then, main controller 20 performs the latter processing offocus calibration as follows. More specifically, as is shown in FIG.11B, while controlling the position of measurement plate 30 (wafer stageWST) in the optical axis direction of projection optical system PL (theZ position), using surface position information measured by Z heads 72a, 72 b, 72 c, and 72 d as a reference as in the former processing offocus calibration, main controller 20 measures an aerial image of ameasurement mark formed on reticle R or on a mark plate (not shown) onreticle stage RST by a Z direction scanning measurement whose detailsare disclosed in, for example, the pamphlet of International PublicationNo. 2005/124834 and the like, using aerial image measurement device 45,and based on the measurement results, measures the best focus positionof projection optical system PL. During the Z direction scanningmeasurement described above, main controller 20 takes in measurementvalues of a pair of Z heads 74 ₃ and 76 ₃ which measure the surfaceposition information at end portions on one side and the other side ofwater table WTB in the X-axis direction, in synchronization with takingin output signals from aerial image measurement device 45. Then, maincontroller 20 stores the values of Z heads 74 ₃ and 76 ₃ correspondingto the best focus position of projection optical system PL in memory(not shown) (or in memory 34). Incidentally, the reason why the position(Z position) related to the optical axis direction Of projection opticalsystem PL of measurement plate 30 (wafer stage WST) is controlled usingthe surface position information measured in the latter processing ofthe focus calibration by Z heads 72 a, 72 b, 72 c, and 72 d is becausethe latter processing of the focus calibration is performed during thefocus mapping previously described.

In this case, because liquid immersion area 14 is formed betweenprojection optical system PL and measurement plate 30 (wafer table WTB)as shown in FIG. 11B, the measurement of the aerial image is performedvia projection optical system PL and the water. Further, although it isomitted in FIG. 11B, because measurement plate 30 and the like of aerialimage measurement device 45 are installed in wafer stage WST, and thelight receiving elements are installed in measurement stage MST, themeasurement of the aerial image described above is performed while waferstage WST and measurement stage MST maintain a contact state (or aproximity state) (refer to FIG. 20).

(c) Accordingly, main controller 20 can obtain the offset at therepresentative detection point of the multipoint AF system (90 a, 90 b),or more specifically, the deviation between the best focus position ofprojection optical system PL and the detection origin of the multipointAF system, based on the relation between the measurement values of Zheads 72 a, 72 b, 72 c, and 72 d (surface position information at theend portions on one side and the other side in the X-axis direction ofwafer table WTB) and the detection results (surface positioninformation) of the measurement plate 30 surface by the multipoint AFsystem (90 a, 90 b) obtained in (a) described above, in the formerprocessing of focus calibration, and also on the measurement values of Zheads 74 ₃ and 76 ₃ (that is, surface position information at the endportions on one side and the other side in the X-axis direction of wafertable WTB) corresponding to the best focus position of projectionoptical system PL obtained in (b) described above, in the latterprocessing of focus calibration. In the embodiment, the representativedetection point is, for example, the detection point in the center ofthe plurality of detection points or in the vicinity thereof, but thenumber and/or the position may be arbitrary. In this case, maincontroller 20 adjusts the detection origin of the multipoint AF systemso that the offset at the representative detection point becomes zeroThe adjustment may be performed, for example, optically, by performingangle adjustment of a plane parallel plate (not shown) insidephotodetection system 90 b, or the detection offset may be electricallyadjusted. Alternatively, the offset may be stored, without performingadjustment of the detection origin. In this case, adjustment of thedetection origin is to be performed by the optical method referred toabove. This completes the focus calibration of the multipoint AF system(90 a, 90 b). Incidentally, because it is difficult to make the offsetbecome zero at all the remaining detection points other than therepresentative detection point by adjusting the detection originoptically, it is desirable to store the offset after the opticaladjustment at the remaining detection points.

Next, offset correction of detection values among a plurality oflight-receiving elements (sensors) that individually correspond to aplurality of detection points of the multiple AF system (90 a, 90 b)(hereinafter, referred to as offset correction among AF sensors) will bedescribed.

On the offset correction among AF sensors, as is shown in FIG. 12A, maincontroller 20 makes irradiation system 90 a of the multipoint AF system(90 a, 90 b) irradiate detection beams to FD bar 46 equipped with apredetermined reference plane, and takes in output signals fromphotodetection system 90 b of the multipoint AF system (90 a, 90 b) thatreceives the reflected lights from the FD bar 46 surface (referenceplane).

In this case, if the FD bar 46 surface is set parallel to the XY plane,main controller 20 can perform the offset correction among AF sensors byobtaining a relation among the detection values (measurement values) ofa plurality of sensors that individually correspond to a plurality ofdetection points based on the output signals loaded in the mannerdescribed above and storing the relation in a memory (or in memory 34),or by electrically adjusting the detection offset of each sensor so thatthe detection values of all the sensors become, for example, the samevalue as the detection value of a sensor that corresponds to therepresentative detection point on the focus calibration described above.

In the embodiment, however, as is shown in FIG. 12A, because maincontroller 20 detects the inclination of the surface of measurementstage MST (integral with FD bar 46) using Z heads 74 ₄, 74 ₅, 76 ₁, and76 ₂ when taking in the output signals from photodetection system 90 bof the multipoint AF system (90 a, 90 b), the FD bar 46 surface does notnecessarily have to be set parallel to the XY plane. In other words, asis modeled in FIG. 12B, when it is assumed that the detection value ateach detection point is the value as severally indicated by arrows inthe drawing, and the line that connects the upper end of the detectionvalues has an unevenness as shown in the dotted line in the drawing,each detection value only has to be adjusted so that the line thatconnects the upper end of the detection values becomes the solid lineshown in the drawing.

Next, a parallel processing operation that uses wafer stage WST andmeasurement stage MST in exposure apparatus 100 of the embodiment willbe described based on FIGS. 13 to 23. Incidentally, during the operationbelow, main controller 20 performs the open/close control of each valveof liquid supply unit 5 of local liquid immersion unit a and liquidrecovery unit 6 in the manner previously described, and water isconstantly filled on the outgoing surface side of tip lens 191 ofprojection optical system PL. However, in the description below, for thesake of simplicity, the explanation related to the control of liquidsupply unit 5 and liquid recovery unit 6 will be omitted. Further, manydrawings are used in the operation description hereinafter, however,reference codes may or may not be given to the same member for eachdrawing. More specifically, the reference codes written are differentfor each drawing; however, such members have the same configuration,regardless of the indication of the reference codes. The same can besaid for each drawing used in the description so far.

FIG. 13 shows a state in which an exposure by the step-and-scan methodof wafer W mounted on wafer stage WST is performed. This exposure isperformed by alternately repeating a movement between shots in whichwafer stage WST is moved to a scanning starting position (accelerationstaring position) to expose each shot area on wafer W and scanningexposure in which the pattern formed on reticle R is transferred ontoeach shot area by the scanning exposure method, based on results ofwafer alignment (EGA: Enhanced Global Alignment) and the like which hasbeen performed prior to the beginning of exposure. Further, exposure isperformed in the following order, from the shot area located on the −Yside on wafer W to the shot area located on the +Y side. Incidentally,exposure is performed in a state where liquid immersion area 14 isformed in between projection unit PU and wafer W.

During the exposure described above, the position (including rotation inthe θz direction) of water stage WST in the XY plane is controlled bymain controller 20, based on measurement results of a total of threeencoders which are the two Y encoders 70A and 70C, and one of the two Xencoders 70B and 70D. In this case, the two X encoders 70B and 70D aremade up of two X heads 66 that face X scale 39X₁ and 39X₂, respectively,and the two Y encoders 70A and 70C are made up of Y heads 65 and 64 thatface Y scales 39Y₁ and 39Y₂, respectively. Further, the Z position androtation (rolling) in the θy direction of wafer stage WST are controlledbased on measurement results of Z heads 74 _(i) and 76 _(j), whichrespectively belong to head units 62C and 62A facing the end section onone side and the other side of the surface of wafer table WTB in theX-axis direction, respectively. The θx rotation (pitching) of waferstage WST is controlled based on measurement values of Y interferometer16. Incidentally, in the case three or more Z heads including Z head 74_(i) and 76 _(i) face the surface of the second water repellent plate 28h of wafer table WTB, it is also possible to control the position ofwafer stage WST in the Z-axis direction, the θy rotation (rolling), andthe θx rotation (pitching), based on the measurement values of Z heads74 _(i), 76 _(i) and the other one head. In any case, the control (morespecifically, the focus leveling control of wafer W) of the position ofwafer stage WST in the Z-axis direction, the rotation in the θydirection, and the rotation in the θx direction is performed, based onresults of a focus mapping performed beforehand.

At the position of water stage WST shown in FIG. 13, while X head 66 ₅(shown circled in FIG. 13) faces X scale 39X₁, there are no X heads 66that face X scale 39X₂. Therefore, main controller 20 uses one X encoder70B and two Y encoders 70A and 70C so as to perform position (X, Y, θz)control of wafer stage WST. In this case, when wafer stage WST movesfrom the position shown in FIG. 13 to the −Y direction, X head 66 ₅moves off of (no longer faces) X scale 39X₁, and X head 66 ₄ (showncircled in a broken line in FIG. 13) faces X scale 39X₂ instead.Therefore, main controller 20 switches the control to a position (X, Y,θz) control of wafer stage WST that uses one X encoder 70D and two Yencoders 70A and 70C.

Further, when wafer stage WST is located at the position shown in FIG.13, Z heads 74 ₃ and 76 ₃ (shown circled in FIG. 13) face Y scales 39Y₂and 39Y₁, respectively. Therefore, main controller 20 performs position(Z, θy) control of wafer stage WST using Z heads 74 ₃ and 76 ₃. In thiscase, when wafer stage WST moves from the position shown in FIG. 13 tothe +X direction, Z heads 74 ₃ and 76 ₃ move off of (no longer faces)the corresponding Y scales, and Z heads 74 ₄ and 76 ₄ (shown circled ina broken line in FIG. 13) respectively face Y scales 39Y₂ and 39Y₁instead. Therefore, main controller 20 switches to position (Z, θy)control of wafer stage WST using Z heads 74 ₄ and 76 ₄.

In this manner, main controller 20 performs position control of waferstage WST by consistently switching the encoder to use depending on theposition coordinate of wafer stage WST.

Incidentally, independent from the position measurement of water stageWST described above using the measuring instrument system describedabove, position (X, Y, Z, θx, θy, θz) measurement of wafer stage WSTusing interferometer system 118 is constantly performed. In this case,the X position and θz rotation (yawing) of wafer stage WST or the Xposition are measured using X interferometers 126, 127, or 128, the Yposition, the θx rotation, and the θz rotation are measured using Yinterferometer 16, and the Y position, the Z position, the θy rotation,and the θz rotation are measured using Z interferometers 43A and 43B(not shown in FIG. 13, refer to FIG. 1 or 2) that constituteinterferometer system 118. Of X interferometers 126, 127, and 128, oneinterferometer is used according to the Y position of wafer stage WST.As indicated in FIG. 13, X interferometer 126 is used during exposure.The measurement results of interferometer system 118 except for pitching(θx rotation) are used for position control of wafer stage WSTsecondarily, or in the case of back-up which will be described later on,or when measurement using encoder system 150 cannot be performed.

When exposure of wafer W has been completed, main controller 20 driveswafer stage WST toward unloading position UP. On this drive, wafer stageWST and measurement stage MST which were apart during exposure come intocontact or move close to each other with a clearance of around 300 μm inbetween, and shift to a scrum state. In this case, the −Y side surfaceof FD bar 46 on measurement table MTB and the +Y side surface of wafertable WTB come into contact or move close together. And by moving bothstages WST and MST in the −Y direction while maintaining the scrumcondition, liquid immersion area 14 formed under projection unit PUmoves to an area above measurement stage MST. For example, FIGS. 14 and15 show the state after the movement.

When wafer stage WST moves further to the −Y direction and moves offfrom the effective stroke area (the area in which wafer stage WST movesat the time of exposure and wafer alignment) after the drive of waferstage WST toward unloading position UP has been started, all the X headsand Y heads, and all the Z heads that constitute encoder 70A to 70D moveoff from the corresponding scale on wafer table WTB. Therefore, positioncontrol of wafer stage WST based on the measurement results of encoders70A to 70D and the Z heads is no longer possible. Just before this, maincontroller 20 switches the control to a position control of wafer stageWST based on the measurement results of interferometer system 118. Inthis case, of the three X interferometers 126, 127, and 128, Xinterferometer 128 is used.

Then, wafer stage WST releases the scrum state with measurement stageMST, and then moves to unloading position UP as shown in FIG. 14. Afterthe movement, main controller 20 unloads wafer W on wafer table WTB. Andthen, main controller 20 drives wafer stage WST in the TX direction toloading position LP, and the next wafer W is loaded on wafer table WTBas shown in FIG. 15.

In parallel with these operations, main controller 20 performs Sec-BCHK(a secondary base line check) in which position adjustment of FD bar 46supported by measurement stage MST in the XY plane and baselinemeasurement of the four secondary alignment systems AL2 ₁ to AL2 ₄ areperformed. Sec-BCHK is performed on an interval basis for every waterexchange. In this case, in order to measure the position (the θzrotation) in the XY plane, Y encoders 70E₂ and 70F₂ previously describedare used.

Next, as shown in FIG. 16, main controller 20 drives wafer stage WST andpositions reference mark FM on measurement plate 30 within a detectionfield of primary alignment system AL1, and performs the former processof Pri-BCHK (a primary baseline check) in which the reference positionis decided for baseline measurement of alignment system AL1, and AL2 ₁to AL2 ₄.

On this process, as shown in FIG. 16, two Y heads 68 ₂ and 67 ₃ and oneX head 66 (shown circled in the drawing) come to race Y scales 39Y₁ and39Y₂, and X scale 39X₂, respectively. Then, main controller 20 switchesthe stage control from a control using interferometer system 118, to acontrol using encoder system 150 (encoders 70F₁, 70E₁, and 70D).Interferometer system 118 is used secondarily again, except inmeasurement of the θx rotation. Incidentally, of the three Xinterferometers 126, 127, and 128, X interferometer 127 is used.

Next, while controlling the position of wafer stage WST based on themeasurement values of the three encoders described above, maincontroller 20 begins the movement of wafer stage WST in the +Y directiontoward a position where an alignment mark arranged in three firstalignment shot areas is detected.

Then, when wafer stage WST reaches the position shown in FIG. 17, maincontroller 20 stops wafer stage WST. Prior to this operation, maincontroller 20 activates (turns ON) Z heads 72 a to 72 d and startsmeasurement of the Z-position and the tilt (the θy rotation) of wafertable WTB at the point in time when all of or part of Z heads 72 a to 72d face (s) wafer table WTB, or before that point in time.

After wafer stage WST is stopped, main controller 20 detects thealignment mark arranged in the three first alignment shot areassubstantially at the same time and also individually (refer to thestar-shaped marks in FIG. 17), using primary alignment system AL1, andsecondary alignment systems AL2 ₂ and AL2 ₃, and makes a link betweenthe detection results of the three alignment systems AL1, AL2 ₂, and AL2₃ and the measurement values of the three encoders above at the time ofthe detection, and stores them in memory (not shown) (or in memory 34).

As in the description above, in the embodiment, the shift to the contactstate (or proximity state) between measurement stage MST and wafer stageWST is completed at the position where detection of the alignment marksof the first alignment shot area is performed. And from this position,main controller 20 begins to move both stages WST and MST in the +Ydirect ion (step movement toward the position for detecting an alignmentmark arranged in five second alignment shot areas) in the contact state(or proximity state). Prior to starting the movement of both stages WSTand MST in the +Y direction, as shown in FIG. 17, main controller 20begins irradiation of a detection beam from irradiation system 90 of themultipoint AF system (90 a, 90 b) to wafer table WTB. Accordingly, adetection area of the multipoint AF System is formed on wafer table WTB.

Then, when both stages WST and MST reach the position shown in FIG. 18during the movement of both stages WST and MST in the +Y direction, maincontroller 20 performs the former process of the focus calibration, andobtains the relation between the measurement values (surface positioninformation on one side and the other side of water table WTB in theX-axis direction) of Z heads 72 a, 72 b, 72 c, and 72 d, in a statewhere the center line of wafer table WTB coincides with reference axisLV, and the detection results (surface position information) of thesurface of measurement plate 30 by the multipoint AF system (90 a, 90b). At this point, liquid immersion area 14 is formed on the uppersurface of FD bar 46.

Then, both stages WST and MST move further in the +Y direction whilemaintaining the contact state (or proximity state), and reach theposition shown in FIG. 19. Then, main controller 20 detects thealignment mark arranged in the five second alignment shot areassubstantially at the same time as well as individually (refer to thestar-shaped marks in FIG. 19), using the five alignment systems AL1, andAL2 ₁ to AL2 ₄, and makes a link between the detection results of thefive alignment systems AL1, and AL2 ₁ to AL2 ₄ and the measurementvalues of the three encoders measuring the position of wafer stage WSTin the XY plane at the time of the detection, and then stores them inmemory (not shown) (or in memory 34). At this point, main controller 20controls the position of wafer stage WST within the XY plane based onthe measurement values of X head 66 ₂ (X linear encoder 70D) that facesX scale 39X₂ and Y linear encoders 70F₁ and 70E₁.

Further, after the simultaneous detection of the alignment marksarranged in the five second alignment shot areas ends, main controller20 starts again movement in the +Y direction of both stages WST and MSTin the contact state (or proximity state), and at the same time, startsthe focus mapping previously described using Z heads 72 a to 72 d andthe multipoint AF system (90 a, 90 b), as is shown in FIG. 19.

Then, when both stages WST and MST reach the position shown in FIG. 20where measurement plate 30 is located directly below projection opticalsystem PL, main controller 20 performs the latter processing of focuscalibration in a state continuing the control of Z position of waferstage WST (measurement plate 30) that uses the surface positioninformation measured by Z heads 72 a, 72 b, 72 c, and 72 d as areference, without switching the Z head used for position (Z position)control of wafer stage WST in the optical axis direction of projectionoptical system PL to Z heads 74 _(t) and 76 _(j).

Then, main controller 20 obtains the offset at the representativedetection point of the multipoint AF system (90 a, 90 b) based on theresults of the former processing and latter processing of focuscalibration described above, and stores the offset in the memory (notshown). And, on reading mapping information obtained from the results offocus mapping at the time of exposure, main controller 20 is to add theoffset to the mapping information.

Incidentally, in the state of FIG. 20, the focus mapping is beingcontinued.

When wafer stage WST reaches the position shown in FIG. 21 by movementin the +Y direction of both stages WST and MST in the contact state (orproximity state) described above, main controller 20 stops wafer stageWST at that position, while making measurement stage MST continue themovement in the +Y direction. Then, main controller 20 detects thealignment mark arranged in the five second alignment shot areassubstantially at the same time as well as individually (refer to thestar-shaped marks in FIG. 21), using the five alignment systems AL1, andAL2 ₁ to AL2 ₄, and makes a link between the detection results of thefive alignment systems AL1, and AL2 ₁ to AL2 ₄ and the measurementvalues of the three encoders at the time of the detection, and thenstores them in the memory (not shown). Further, at this point as well,the focus mapping is being continued.

Meanwhile, after a predetermined period of time from the suspension ofwafer stage WST described above, measurement stage MST and wafer stageWST move from the contact state (or proximity state) into a separationstate. After moving into the separation state, main controller 20 stopsthe movement of measurement stage MST when measurement stage MST reachesan exposure start waiting position where measurement stage MST waitsuntil exposure is started.

Next, main controller 20 starts the movement of wafer stage WST in the+Y direction toward a position where the alignment mark arranged in thethree fourth alignment shots are detected. At this point in time, thefocus mapping is being continued. Meanwhile, measurement stage MST iswaiting at the exposure start waiting position described above.

Then, when wafer stage WST reaches the position shown in FIG. 22, maincontroller 20 immediately stops wafer stage WST, and almostsimultaneously and individually detects the alignment marks arranged inthe three fourth alignment shot areas on wafer W (refer to star-shapedmarks in FIG. 22) using primary alignment system AL1 and secondaryalignment systems AL2 ₂ and AL2 ₃, links the detection results of threealignment systems AL1, AL2 ₂ and AL2 ₃ and the measurement values of thethree encoders out of the four encoders above at the time of thedetection, and stores them in memory (not shown). Also at this point intime, the focus mapping is being continued, and measurement stage MST isstill waiting at the exposure start waiting position. Then, using thedetection results of a total of 16 alignment marks and the measurementvalues of the corresponding encoders obtained in the manner describedabove, main controller 20 computes array information (coordinate values)of all the shot areas on wafer W on an alignment coordinate system (anXY coordinate system whose origin is placed at the detection center ofprimary alignment system AL1) that is set by the measurement axes ofencoders 70B, 70D, 70E₁, and 70F₁ of encoder system 150, by performing astatistical computation disclosed in, for example, U.S. Pat. No.4,780,617 and the like.

Next, main controller 20 continues the focus mapping while moving waferstage WST in the +Y direction again. Then, when the detection beam fromthe multipoint AF system (90 a, 90 b) begins to miss the water Wsurface, as is shown in FIG. 23, main controller 20 ends the focusmapping.

After the focus mapping has been completed, main controller 20 moveswafer stage WST to a scanning starting position (acceleration startingposition) for exposure of the first shot on wafer W, and during themovement, main controller 20 switches the Z heads used for control ofthe Z position and the θy rotation of wafer stage WST from Z heads 72 ato 72 d to Z heads 74 _(i) and 74 _(j) while maintaining the Z position,the θy rotation, and the θx rotation of wafer stage WST. After thisswitching, based on the results of the wafer alignment (EGA) previouslydescribed and the latest baselines and the like of the five alignmentsystems AL1 and AL2 ₁ to AL2 ₄, main controller 20 performs exposure bya step-and-scan method in a liquid immersion exposure, and sequentiallytransfers a reticle pattern to a plurality of shot areas on wafer W.Hereinafter, a similar operation is performed repeatedly.

Next, a computation method of the Z position and the amount of tilt ofwafer stage WST using the measurement results of the Z heads will bedescribed Main controller 20 uses the four Z heads 70 a to 70 d thatconstitute surface position measurement system 180 (refer to FIG. 6) atthe time of focus calibration and focus mapping, and measures height Zand tilt (rolling) θy of wafer table WTB. Further, main controller 20uses two Z heads 74 _(j) and 76 _(j) (i and j are one of 1 to 5) at thetime of exposure, and measures height Z and tilt (rolling) θy of wafertable WTB. Incidentally, each Z head irradiates a probe beam on theupper surface (a surface of a reflection grating formed on the uppersurface) of the corresponding Y scales 39Y₁ or 39Y₂, and measures thesurface position of each scale (reflection grating) by receiving thereflected light.

FIG. 24A shows a two-dimensional plane having height Z₀, rotation angle(an angle of inclination) around the X-axis θx, and rotation angle (anangle of inclination) around the Y-axis θy at a reference point O.Height z at position (X, Y) of this plane is given by a functionaccording to the next formula (8).

f(X,Y)=−tan θy·X+tan θx·Y+Z ₀  (8)

As shown in FIG. 24B, at the time of the exposure, height Z from amovement reference surface (a surface that is substantially parallel tothe XY plane) of water table WTB and rolling θy are measured at anintersection point (reference point) O of a movement reference surfaceof wafer table WTB and optical axis AX of projection optical system PL,using two Z heads 74 _(i) and 76 _(j) (i and j are one of 1 to 5). Inthis case, Z heads 74 ₃ and 76 ₃ are used as an example. Similar to theexample shown in FIG. 24A, the height of wafer table WTB at referencepoint O will be expressed as Z₀, the tilt (pitching) around the X-axiswill be expressed as ex, and the tilt (rolling) around the Y-axis willbe expressed as θy. In this case, measurement values Z_(L) and Z_(R) ofthe surface position of (reflection gratings formed on) Y scales 39Y₂and 39Y₁ indicated by Z head 74 ₃, which is located at coordinate(p_(L), q_(L)), and Z head 76 ₃, which is located at coordinate (p_(R),q_(R)) in the XY plane, respectively, follow theoretical formulas (9)and (10), similar to formula (8).

Z _(L)=−tan θ·p _(L)+tan θx·q _(L) +Z ₀  (9)

Z _(R)=−tan θy·p _(R)+tan θx·q _(R) +Z ₀  (10)

Accordingly, from theoretical formulas (9) and (10), height Z₀ of wafertable WTB and rolling θy at reference point O can be expressed as in thefollowing formulas (11) and (12), using measurement values Z_(L) andZ_(R) of Z heads 74 ₃ and 76 ₃.

Z ₀ ={Z _(L) +Z _(R)−tan θx·(q _(L) +q _(R))}/2  (11)

tan θy={Z _(L) −Z _(R)−tan θx·(q _(L) −q _(R))}/(p _(R) −p _(L))  (12)

Incidentally, in the case of using other combinations of Z heads aswell, by using theoretical formulas (11) and (12), height Z₀ of wafertable WTB and rolling θy at reference point O can be computed. However,pitching θx uses the measurement results of another sensor system (inthe embodiment, interferometer system 118).

As shown in FIG. 24B, at the time of focus calibration and focusmapping, height Z of wafer table WTB and rolling θy at a center point O′of a plurality of detection points of the multipoint AF system (90 a, 90b) are measured, using four Z heads 72 a to 72 d. Z heads 72 a to 72 d,in this case, are respectively placed at position (X, Y)=(p_(a), q_(a)),(p_(b), q_(b)), (p_(c), q_(c)), (p_(d), q_(d)). As shown in FIG. 24B,these positions are set symmetric to center point O′=(Ox′, Oy′), or morespecifically, p_(a)=p_(b), p_(c)=p_(d), q_(a)=q_(c), q_(b)=q_(d), andalso (p_(a)+p_(c))/2=(p_(b)+p_(d))/2=Ox′,(q_(a)+q_(b))/2=(q_(c)+q_(d))/2=Oy′.

From average (Za+Zb)/2 of measurement values Za and Zb of Z head 72 aand 72 b, height Ze of wafer table WTB at a point e of position(p_(a)=p_(b), Oy′) can be obtained, and from average (Zc+Zd)/2 of themeasurement values Zc and Zd of Z heads 70 c and 70 d, height Zf ofwafer table WTB at a point f of position (p_(c)=p_(d), Oy′) can beobtained. In this case, when the height of wafer table WTB at centerpoint O′ is expressed as Z₀, and the tilt (rolling) around the Y-axis isexpressed as θy, then, Ze and Zf follow theoretical formulas (13) and(14), respectively.

Ze{=(Z _(a) +Z _(b))/2}=−tan θy·(p _(a) +p _(b)−20x′)/2+Z ₀  (13)

Zf{=(Z _(c) +Z _(d))/2}=−tan θy·(p _(c) +p _(d)−20x′)/2+Z ₀  (14)

Accordingly, from theoretical formulas (13) and (14), height Z₀ of watertable WTB and rolling θy at center point O′ can be expressed as in thefollowing formulas (15) and (16), using measurement values Za to Zd of Zheads 70 a to 70 d.

$\begin{matrix}{Z_{0} = {{( {{Ze} + {Zf}} )/2} = {( {{Za} + {Zb} + {Zc} + {Zd}} )/4}}} & (15) \\\begin{matrix}{{\tan \; \theta \; y} = {{- 2}{( {{Ze} - {Zf}} )/( {p_{a} + p_{b} - p_{c} - p_{d}} )}}} \\{= {{- ( {{Za} + {Zb} - {Zc} - {Zd}} )}/( {p_{a} + p_{b} - p_{c} - p_{d}} )}}\end{matrix} &  (16) )\end{matrix}$

However, pitching θx uses the measurement results of another sensorsystem (in the embodiment, interferometer system 118).

As shown in FIG. 16, immediately after switching from servo control ofwafer stage WST by interferometer system 118 to servo control by encodersystem 150 (encoders 70A to 70F) and surface position measurement system180 (Z head systems 72 a to 72 d, 74 ₁ to 74 ₅, and 76 ₁ to 76 ₅),because only two heads, Z heads 72 b and 72 d, face the corresponding Yscales 39Y₁ and 39Y₂, the Z and θy positions of wafer stage WST atcenter point O′ cannot be computed using formulas (15) and (16). In sucha case, the following formulas (17) and (18) are applied.

Z ₀ ={Z _(b) +Z _(d)−tan θx·(q _(b) +q _(d)−20y′)}/2  (17)

tan θy={Z _(b) −Z _(d)−tan θx·(q _(b) −q _(d))}/(p _(d) −p _(b))  (18)

Then, when wafer stage WST has moved in the +Z direction, andaccompanying this move, after Z heads 72 a and 72 c have faced thecorresponding Y scales 39Y₁ and 39Y₂, formulas (15) and (16) above areapplied.

As previously described, scanning exposure to wafer W is performed,after finely driving wafer stage WST in the Z-axis direction and tiltdirection according to the unevenness of the surface of wafer W, andhaving adjusted the surface position of wafer W and the tilt (focusleveling) so that the exposure area IA portion on the surface of wafer Wmatches within the range of the depth of focus of the image plane ofprojection optical system PL. Therefore, prior to the scanning exposure,focus mapping to measure the unevenness (a focus map) of the surface ofwafer W is performed. In this case, as shown in FIG. 10B, the unevennessof the surface of wafer W is measured at a predetermined samplinginterval (in other words, a Y interval) while moving wafer stage WST tinthe +Y direction, using the multipoint AF system (90 a, 90 b) with thesurface position of wafer table WTB (or to be more precise, thecorresponding Y scales 39Y₁ and 39Y₂) measured using Z heads 72 a to 72d serving as a reference.

To be specific, as shown in FIG. 24B, surface position Ze of wafer tableWTB at point e can be obtained from the average of surface positions Zaand Zb of Y scale 39Y₂, which is measured using Z heads 72 a and 72 b,and surface position Zf of wafer table WTB at point f can be obtainedfrom the average of surface positions Zc and Zd of Y scale 39Y₁, whichis measured using Z heads 72 c and 72 d. In this case, the plurality ofdetection points of the multipoint AF system and center O′ of thesepoints are located on a straight line ef parallel to the X-axis andconnecting point e and point f. Therefore, as shown in FIG. 10C, byusing a straight line expressed tin the following formula (19)connecting surface position Ze at point e (P1 in FIG. 10C) of wafertable WTB and surface position Zf at point f (P2 in FIG. 10C) as areference, surface position Z_(0k) of the surface of wafer W atdetection point X_(k) is measured, using the multipoint AF system (90 a,90 b).

Z(X)=−tan θy·X+Z ₀  (19)

However, Z₀ and tansy can be obtained from formulas (15) and (16) above,using measurement results Za to Zd of Z heads 72 a to 72 d. From theresults of surface position Z_(0k) that has been obtained, unevennessdata (focus map) Z_(k) of the surface of wafer W can be obtained as inthe following formula (20).

Z _(k) =Z _(0k) −Z(X _(k))  (20)

At the time of exposure, by finely driving wafer stage WST in the Z-axisdirection and the tilt direction according to focus map Z_(k) obtainedin the manner described above, focus is adjusted, as is previouslydescribed. At the time of the exposure here, the surface position ofwafer table WTB (or to be more precise, the corresponding Y scales 39Y₂and 39Y₁) is measured, using Z heads 74 _(i) and 76 _(j) (i, j=1-5).Therefore, reference line Z(X) of focus map Z_(k) is set again. However,Z₀ and tan θy can be obtained from formulas (11) and (12) above, usingthe measurement results Z_(L) and Z_(R) of Z heads 74 _(i) and 76 _(j)(i, j=1-5). From the procedure described so far, the surface position ofthe surface of wafer W is converted to Z_(k)+Z(X_(k)).

In exposure apparatus 100 of the embodiment, as shown in FIGS. 25A and25B, in the effective stroke range (a range where the stage moves foralignment, exposure operation, and focus mapping) of wafer stage WST,the Z heads are placed so that at least one of Z heads 76 _(j) and 74_(i) (j and i are one of 1 to 5) or one of 72 a to 72 d faces each ofthe Y scales 39Y₁ and 39Y₂, without fail. In FIGS. 25A and 25B, the Zhead which faces the corresponding Y scale is shown surrounded in acircle.

In this case, when wafer stage WST is to be driven in a directionindicated by an outlined arrow (the +X direction) as shown in FIG. 25A,as indicated by arrow f1, the Z head which faces Y scale 39Y₂ isswitched from Z head 74 ₃ shown circled by a solid line to a Z head 74 ₄which is shown circled by a dotted line. Further, when wafer stage WSTis to be driven furthermore in a direction indicated by an outlinedarrow (the +X direction) as shown in FIG. 25B, as indicated by arrow f2,the Z head which faces Y scale 39Y₁ is switched from Z head 76 ₃ showncircled by a solid line to a Z head 76 ₄ which is shown circled by adotted line. In this manner, Z heads 74 _(i) and 76 _(j) (i, j=1-5) aresequentially changed to the next head, with the movement of wafer stageWST in the X-axis direction. Incidentally, at the time of switching ofthe Z head, a return process in which setting of the reference surfaceposition (the origin) and measurement preparation are performed, orfurthermore, a linkage process to keep the continuity of the measurementresults, is performed. Details on these processes will be describedlater in the description.

Next, a switching procedure of the Z head will be described, based onFIGS. 26A to 26E and also appropriately using other drawings as areference, taking the switching from Z head 76 ₃ to 76 ₄ shown in arrowf2 in FIG. 25B as an example. In FIG. 26A, a state before the switchingis shown. In this state, Z head 76 ₃ facing the scanning area (the areawhere the diffraction grating is arranged) on Y scale 39Y₁ is operating,and Z head 76 ₄ which has moved away from the scanning area issuspended. Here, the operating (focus servo) Z heads are shown in ablack circle, and the suspended or waiting (scale servo) Z heads areshown in an outlined circle, respectively. Based on measurement valuesof the operating Z head 76 ₃, main controller 20 computes the positionof wafer stage WST. In this case, the Z head used for computing theposition of wafer stage WST is shown surrounded by a double circle.

When wafer stage WST moves in the +X direction from the state shown inFIG. 26A, Y scale 39Y₁ is displaced in the +X direction, and Z head 76 ₄which is suspended approaches the scanning area on Y scale 39Y₁. Then,main controller 20 confirms that Z head 76 ₄ has come within apredetermined distance from the scanning area, and performs the returnprocess of Z head 76 ₄.

Now, the return process of Z head 76 ₄ will be described, referring toFIGS. 27A to 27C. As shown in FIG. 27A, reference surface position(origin) S₀ of Z head 76 ₄ is to be set at the time of initial operationof the Z head, such as during the start up of exposure apparatus 100 asis previously described.

Main controller 20 estimates a predicted value (more specifically, apredicted surface position S of Y scale 39Y₁) of the measurement valueof Z head 76 ₄, which is to be restored from function t (X, Y) of theformula (8) previously described, using the position of wafer stage WSTin directions of three degree of freedom (Z, θy, θx) obtained from themeasurement results of the operating Z head and interferometer system118. Now, into X and Y, the X and Y positions of Z head 76 ₄ aresubstituted. And, as shown in FIG. 27B, main controller 20 displaces Zsensor main section ZH via the drive section (not shown) in Z head 76 ₄so that the measurement value of Z head 76 ₄ matches a predicted value(Z head 76 ₄ outputs a predicted value which serves as a measurementvalue), and makes the focal point of probe beam LB coincide withpredicted surface position S.

In the state where the return process described above has beencompleted, the focal position of probe beam LB coincides with predictedsurface position S of Y scale 39Y₁. Incidentally, with the movement ofwafer stage WST in directions of three degree of freedom (Z, θy, θx),predicted surface position S of Y scale 39Y₁ is also displaced. And,following the displacement, sensor main section ZH of Z head 76 ₄ alsoperforms Z displacement. More specifically, Z head 76 ₄ performs afollow-up servo (scale servo) with respect to predicted surface positionS of Y scale 39Y₁. Z head 76 ₄ is waiting in such a state.

In this case, in the embodiment, as is previously described, thedistance in the X-axis direction between the two adjacent Z heads 74_(i) and 76 _(j) is set smaller than the effective width (width of thescanning area) of Y scales 39Y₂ and 39Y₁ in the X-axis direction.Therefore, a state occurs when Z heads 76 ₃ and 76 ₄ simultaneously facethe scanning area of Y scale 39Y₁ as shown in view 26B. Therefore, aftermain controller 20 confirms that Z head 76 ₄ in a waiting (a scaleservo) state has faced the scanning area along with the operating Z head76 ₃ as shown in FIG. 26B, main controller 20 begins focus servo withrespect to the actual surface position of Y scale 39Y₁ of Z head 76 ₄,as shown in FIG. 27C.

However, in the waiting (during scale servo to the predicted surfaceposition) state, focus error (hereinafter simply referred to as anoutput, as appropriate) I which is the output of focus sensor ES ismonitored. If output I becomes zero, it can be judged that the predictedsurface position (more specifically, the Z position of the focus of theprobe beam of the Z head) of Y scale 39Y₁ matches the actual surfaceposition. Therefore, main controller 20 begins the focus servo, afterconfirming that Z heads 76 ₃ and 76 ₄ have faced the scanning area of Yscale 39Y₁, and at the same time, that output I of focus sensor FS hasbecome zero or approximately 0 (a value which is equal to or less than apredetermined value, and can be substantially regarded as zero) asdescribed above. By performing the processing of such a procedure, the Zhead can be shifted smoothly from scale servo to focus servo. However,at this point, while the measurement value of Z head 76 ₄ is monitored,it is not used in position computation (position control) of wafer tableWTB (wafer stage WST).

Next, as shown in FIG. 26C, while Z head 76 ₃ which is to be suspendedlater faces the scanning area, main controller 20 switches the Z headused to compute the position of wafer stage WST in directions of twodegrees of freedom (Z, θy) from Z head 76 ₃ to 76 ₄. However, in thisprocessing, the position of wafer stage WST in directions of two degreesof freedom (Z, θy) computed before and after the switching generallybecomes discontinuous. Therefore, a linkage process of the measurementvalues which will be described later is performed, as necessary. Afterthe linkage process has been completed, the Z head to be used isswitched from Z head 76 ₃ to 76 ₄. After the switching has beencompleted, as shown in FIG. 26D, main controller 20 rakes Z head 76 ₃move into a waiting (scale servo) state before moving off of thescanning area, and then, when Z head 76 ₃ is sufficiently distanced fromthe scanning area, suspends its operation. With the operation describedabove, the switching of the Z head is completed, and hereinafter, asshown in FIG. 26E, Z head 76 ₄ is used.

In the embodiment, the spacing between adjacent Z heads 74 (i=1 to 5),for example, is 70 mm (with some exceptions), and is set smaller thanthe effective width of the scanning area of Y scale 39Y₂ in the X-axisdirection, which is, for example, 76 mm. Further, similarly, the spacingbetween adjacent Z heads 76 _(j) (j=1 to 5) is, for example, 70 mm (withsome exceptions), and is set smaller than the effective width of thescanning area of Y scale 39Y₁ in the X-axis direction, which is, forexample, 76 mm. Because of this, the switching of Z heads 74 _(i) and 76_(j) (i, j=1-5) can be carried out smoothly, as described above.

Incidentally, the range in which the two adjacent Z heads face thescale, or more specifically, the moving distance of wafer stage WST(wafer table WTB) from a state shown in FIG. 26B to a state shown inFIG. 26D, for example, is 6 mm. And at the center, or more specifically,when wafer stage WST is located at the position shown in FIG. 26C, the Zhead that monitors the measurement values is switched. This switchingoperation is completed by the time the Z head which is to be suspendedmoves off the scanning area, or more specifically, while wafer stage WSTmoves in an area by a distance of 3 mm during the state shown in FIG.26C until the state shown in FIG. 26D. Incidentally, in the case themovement speed of the stage is 1 m/sec, then the switching operation ofthe Z head is to be completed within 3 msec.

Next, the linkage process at the time of switching of the Z heads 72 ato 72 d, 74 ₁ to 74 ₅, and 76₁ to 76₅, or more specifically, the resetof the measurement values to maintain the continuity of the position ofwafer stage WST in directions of two degrees of freedom (Z, θy) computedby the measurement results of the Z heads will be described, focusingmainly on the operation of main controller 20.

In the embodiment, as is previously described, in the movement strokerange of wafer stage WST at the time of exposure, at least two Z headsZsL (one of 74 ₁ to 74 ₅) and ZsR (one of 76 ₁ to 76 ₅) constantlyobserve the movement of wafer stage WST. Accordingly, when the switchingprocess of the Z head is performed, three Z heads, to which a third Zhead ZsR′ is added to the two Z heads ZsL and ZsR, will be made toobserve wafer stage WST as shown in FIG. 28A. In this case, Z heads ZsL,ZsR, and ZsR′ are located above Y scales 39Y₂, 39Y₁, and 39Y₁,respectively, and are performing follow-up servo (focus servo) of thesurface positions.

In the embodiment, as shown in FIG. 28A, main controller 20 switchesfrom position (Z, θy) measurement of wafer stage WST by the two Z headsZsL and ZsR to position (Z, θy) measurement of wafer stage WST by thetwo Z heads ZsL and ZsR′. On this switching, first of all, maincontroller 20 substitutes measurement values Z_(L) and Z_(R) of Z headsZsL and ZsR, to which offset cancellation to be described later havebeen performed, into formulas (11) and (12) and computes Z₀ and θypositions of wafer stage WST at reference point O (an intersecting pointof the movement reference surface of wafer stage WST and optical axis AXof projection optical system PL). Next, using the Z0 and θy positionscomputed here, and the θx position measured by interferometer system118, a predicted value ZR′ of the third Z head ZsR′ is obtainedaccording to theoretical formula (10). Now, the X position (p_(R′)) andY position (q_(R′)) of Z head ZsR′ are substituted into pR and qR. Andoffset O_(R′)=Z_(R′)−Z_(R0′) is set. In this case, Z_(R0′) is the actualmeasurement value of Z head ZsR′, that is, the actual measurement resultof the surface position of the opposing Y scale 39Y₁. Measurement valueZ_(R′) of Z head ZsR′ is given by performing offset correction usingoffset O_(R′) on the actual measurement value Z_(R0′), namely by thefollowing formula (21).

Z _(R′) =Z _(R0′) +O _(R′)  (21)

By the handling using offset O_(R′), predicted value Z_(R′) is set asmeasurement value Z_(R′) of Z head ZsR′.

By the linkage process described above, the switching operation of the Zhead is completed while having maintained the position (Z₀, θy) of waferstage WST. From then onward, from formulas (11) and (12), positioncoordinate (Z₀, θy) of wafer stage WST is computed, using measurementvalues Z_(L) and Z_(R′) of Z heads ZsL and ZsR′ which are used after theswitching. However, in formula (11) and formula (12), Z_(R′), p_(R′),q_(R′) are substituted into Z_(R), p_(R), q_(R).

Z _(L′) =Z _(L0′) +O _(L′)  (22)

By the handling using offset O_(L′), predicted value Z_(L′) is set asmeasurement value Z_(L′) of Z head ZsL′.

By the linkage process described above, the switching operation of the Zhead is completed while having maintained the position (Z₀, θy) of waferstage WST. From then onward, from formulas (11) and (12), positioncoordinate (Z₀, θy) of wafer stage WST is computed, using measurementvalues Z_(L′) and Z_(R) of Z heads ZsL′ and ZsR which are used after theswitching. However, in formula (11) and formula (12), Z_(L′), p_(L′),q_(V)′ are substituted into Z_(L), p_(L), q_(L).

However, in the actual measurement value (raw measurement value) of Zhead ZsR′ or ZsL′, various measurement errors are included. Therefore,main controller 20 shows the value whose error has been corrected as ameasurement value. Accordingly, in the linkage process described above,main controller 20 uses scale unevenness error correction information,correction information on the Z head installation error and the like,and performs an inverse correction of the theoretical value obtainedfrom formulas (9) and (10) and computes the raw value before correction,and then sets the raw value as the measurement value of Z head ZsR′ orZsL′. Incidentally, it is convenient to include such error correctioninformation in offset O_(R′) and O_(L′) described above, and to performerror correction simultaneously with the offset correction (formulas(21) and (22)).

Incidentally, by applying the coordinate linkage method, the position(Z, θy) of wafer stage WST which is computed before and after theswitching of the Z heads becomes continuous without fail. However, anerror (a linkage error) may occur, due to the prediction calculation ofthe measurement value, the offset computation and the like of the Z headto be newly used. When exposure of all the shot areas on the wafer isactually performed, the switching of the encoder will be performed, forexamples approximately 100 times. Accordingly, even if the error whichoccurs in one linkage process is small enough to ignore, the errors maybe accumulated by repeating the switching many times, and may come toexceed a permissible level. Incidentally, assuming that the errors occurat random, the cumulative error which occurs by performing the switching100 times is about 10 times the error which occurs when the switching isperformed once. Accordingly, the precision of the linkage process mustbe improved as much as possible, and a stage control method which is notaffected by the linkage accuracy will have to be employed.

Therefore, for example, position control of wafer stage WST ispreferably performed using the position coordinate (Z, θy) of waferstage WST which has been obtained by applying the coordinate linkagemethod, and focus calibration and a focus should be performed using theposition coordinate (Z, θy) of wafer stage WST which has been obtainedfrom the actual output of the Z head, without applying the coordinatelinkage method. Further, when the wafer stage WST stops, the offsetshould be cleared to cancel out the accumulated linkage error.

The position coordinate of wafer stage WST is controlled, for example,at a time interval of 96 μsec. At each control sampling interval, maincontroller 20 updates the current position of wafer stage WST, computesthrust command values and the like to position the stage to a targetposition, and outputs the values. As previously described, the currentposition of wafer stage WST is computed from the measurement results ofinterferometer system 118, encoder system 150 (encoders 70A to 70F), andsurf ace position measurement system 180 (Z heads 72 a to 72 d, 74 ₁ to74 ₅, and 76 ₁ to 76 ₅). Accordingly, main controller 20 monitors themeasurement results of the interferometer, the encoder, and the Z headsat a time interval (measurement sampling interval) much shorter than thecontrol sampling interval.

Therefore, in the embodiment, main controller 20 constantly continues toreceive the measurement values from all the Z heads (not always two)that face the scanning area (the area where the probe beams from the Zheads are scanned) of the scales, while wafer stage WST is within theeffective stroke range. And, main controller 20 performs the switchingoperation (a linkage operation between a plurality of Z heads) of the Zheads described above in synchronization with position control of waferstage WST which is performed at each control sampling interval. In suchan arrangement, an electrically high-speed switching operation of the Zheads will not be required, which also means that costly hardware torealize such a high-speed switching operation does not necessarily haveto be arranged.

FIG. 29 conceptually shows the timing of position control of water stageWST, the uptake of the measurement values of the Z head, and theswitching of the Z head in the embodiment. Reference code CSCK in FIG.29 indicates the generation timing of a sampling clock (a control clock)of the position control of wafer stage WST, and reference code MSCKindicates a generation timing of a sampling clock (a measurement clock)of the measurement of the Z head (and interferometer and encoder).Further, reference code CH typically shows the switching (linkage) ofthe Z head described in detail in FIG. 26.

Main controller 20 executes the switching of the Z heads by dividing theoperation into two stages; the restoration process and the switchingprocess (and the linkage process) of the Z heads. When describing theswitching according to an example shown in FIG. 29, first of all, the Zheads which are operating at the time of the first control clock are tobe of a first combination, ZsL and ZsR. Main controller 20 monitors themeasurement value of these Z heads, and computes the position coordinate(Z, θy) of wafer stage WST. Next, according to the position coordinateof water stage WST, main controller 20 obtains all the Z heads which areabove and in the vicinity of the scanning area of the Y scale, and fromthese heads, main controller 20 specifies Z head ZsR′ which needsrestoration, and restores the encoder at the time of the second controlclock. In this case, Z head ZsR′ which has been restored is in thewaiting state (scale servo state) previously described, and is switchedto the operating state (focus servo state) after main controller 20confirms that Z head ZsR′ has faced the scanning area of the Y scale. Atthis point of time, the operating Z heads become three, which are, ZsL,ZsR and ZsR′. And then, main controller 20 specifies the Z head whosemeasurement values are to be monitored to compute the positioncoordinate of wafer stage WST at the time of the next control clock fromthe operating Z heads, according to the position coordinate of waferstage WST. Assume that a second combination ZsL and ZsR′ are specifiedhere. Main controller 20 confirms whether this specified combinationmatches the combination that was used to compute the position coordinateof wafer stage WST at the time of the previous control clock. In thisexample, Z head ZsR in the first combination and Z head ZsR′ in thesecond combination are different. Therefore, main controller 20 performsa linkage process CH to the second combination at the time of the thirdcontrol clock. Hereinafter, main controller 20 monitors the measurementvalues of the second combination ZsL and ZsR′, and computes the positioncoordinate (Z, θy) of wafer stage WST. As a matter of course, linkageprocess CH is not performed if there is no change in the combination. Zhead ZsR which is removed from the monitoring subject, is switched to awaiting state at the time of the fourth control clock when Z head ZsRmoves off from the scanning area on the Y scale.

Incidentally, so far, in order to describe the principle of theswitching method of the encoder to be used in position control of waferstage WST in the embodiment, four Z heads ZsL, ZsL′, ZsR, and ZsR′ weretaken up, however, ZsL and ZsL′ representatively show any of Z heads 74_(i) (i=1 to 5), 72 a, and 72 b, and ZsR and ZsR′ representatively showany of Z heads 76 _(j) (j=1 to 5), 72 c, and 72 d. Accordingly, similarto the switching between Z heads 74 _(i) (i=1 to 5) and 76 j (j=1 to 5),the switching and linkage process described above can be applied to theswitching between Z heads 72 a to 72 d, and the switching between Zheads 72 a to 72 d and Z heads 74 _(i) (i=1 to 5), 76 _(j) (j=1 to 5).

By at least a part of the measurement beam being intercepted (this makesdetection of a foreign material possible, therefore, in the descriptionbelow, it will also be expressed as detecting a foreign material) by aforeign material adhered on the scale surface and the like, abnormalitymay occur in the measurement results of the encoder (X heads and Yheads) and the Z heads. In this case, the measurement beam of theencoder has an expanse of 2 mm in the measurement direction and 50 μm inthe grid line direction on the scale surface. The probe beam of the Zhead is condensed to several μm on the diffraction grating surfaceserving as a reflection surface, however, on the scale surface, theprobe beam widens to an extent of sub millimeters according to thenumerical aperture at the scale surface (the cover glass surface).Accordingly, even a small foreign material can be detected. Furthermore,in a practical point of view, it is extremely difficult to completelyprevent foreign materials from entering the device and from adhering onthe scale surface for over a long period. Further, a situation can beconsidered where the encoder or the Z head fails to work properly, andthe encoder output is cut off. Therefore, when abnormality occurs in themeasurement results of the encoder and/or the Z head, a backup operationsuch as to switch the measurement to a measurement by interferometersystem 118 from measurement by the encoder and/or the Z head in whichabnormality has occurred, or to correct the measurement results of theencoder and/or the Z head in which abnormality has occurred using themeasurement results of interferometer system 118 becomes necessary.

In the case of exposure apparatus 100 in the embodiment, water dropletsmay remain on the scale surface. For example, the liquid immersion areafrequently passes over scale 39X₁ of wafer stage WST which is adjacentto measurement stage MST when wafer stage WST and measurement stage MSTform a scrum. Further, as for the other scales as well, at the time ofedge shot exposure, the liquid immersion area enters a part of an areaon the scale. Accordingly, the water droplets that cannot be recoveredand are left on the scale may be a source which generates abnormality inthe measurement results of the encoder and/or the Z head. In this case,when the encoder and/oz the Z head detect water droplets, the beam isblocked by the water droplets which reduces the beam intensity, andfurthermore, the output signals are cut off (however, the output of themeasurement section of the Z head is different from the output of thefocus sensor, and is not cut off due to the presence of water droplets).Furthers because materials of a different refractive index are detected,linearity of the measurement results with respect to the displacement ofwafer stage WST (wafer table WTB) deteriorates. The reliability of themeasurement results should be inspected, on the basis of such variousinfluences.

The abnormality of the measurement results of the encoder or the Z headcan be determined from sudden temporal change of the measurementresults, or from deviation or the like of the measurement results fromthe measurement results of a different sensor. First of all, in theformer case, when the position coordinates of wafer stage WST obtainedat every measurement sampling interval using the encoders or the Z headchange so much from the position coordinates obtained at the time of theprevious sampling that it cannot be possible when taking intoconsidering the actual drive speed of the stage, main controller 20decides that abnormality has occurred. In the latter case, maincontroller 20 predicts the individual measurement values of the encoderor the Z head from the current position of wafer stage WST, and when thedeviation of the predicted measurement values from the actualmeasurement values exceeds a permissible level which is decided inadvance, main controller 20 decides that abnormality has occurred.Further, in the embodiment, position measurement using interferometersystem 118 is performed in the whole stroke area, independently from theposition measurement of wafer stage WST using the encoder and the Zhead. Therefore, in the case the deviation of the position coordinatesof wafer stage WST obtained using the encoder or the Z head from theposition coordinates of wafer stage WST obtained using interferometersystem 118 exceeds a permissible level which is decided in advance, maincontroller 20 decides that abnormality has occurred.

By the Z head detecting, for example, a foreign material adhered on thescale surface, abnormal measurement results can be output. However, insuch a case, by the movement of wafer stage WST, the output of the Zhead promptly returns to the normal output. Next, a response to such atemporary abnormality output will be described.

First of all, main controller 20 predicts the measurement value of the Zhead, that is, the surface position of the corresponding Y scale(measurement surface), from theoretical formulas (9) and (10) using thecurrent position (Z, θx, θy) of wafer stage WST. By obtaining thedifference between the predicted measurement value and the actualmeasurement value of the Z head, and furthermore, taking the average (orto be more precise, a movement average covering a predetermined numberof control clocks) regarding a predetermined timer main controller 20obtains offset Oz. This offset Oz is set to all the Z heads, and is usedas an index to inspect the measurement results of the individual Zheads.

Now, a case will be considered where a Z head ZS detects a foreignmaterial DW, which is adhered on a moving measurement target surface S0,as shown in FIGS. 30A to 30H. First of all, as shown in FIG. 30A, Z headZS is to be in an operating state, or more specifically, in a focusservo state where the surface position of measurement target surface S₀is followed. As previously described, the reflected light of probe beamLB is received by tetrameric light receiving element ZD whichconstitutes focus sensor FS. In the operating state, as shown in FIG.30B, sensor main section ZH including focus sensor FS follows thesurface position of measurement target surface S₀ so that the sectionalshape of the reflected light of probe beam LB is in the form of a circleon the detection surface of tetrameric light receiving element ZD, ormore specifically, so that focus error I of focus sensor FS expressed informula (7) becomes zero (I=0). At this point in time, measurementsection ZE outputs a reading value E₀ corresponding to the surfaceposition of measurement target surface S₀ as a measured value of Z headZS.

Next, measurement target surface S₀ moves in the −Y direction from theposition shown in FIG. 30A, and assume that Z head ZS detects foreignmaterial DW adhering on the surface, as shown in FIG. 30C. In this case,for the sake of simply, assume that probe beam LB is completelyreflected on the surface of foreign material DW, and the principal rayof the reflected light matches the principal ray of probe beam LB. Atthis point, sensor main section ZH follows the actual reflectionsurface, or more specifically, follows surface S of foreign material DWso as to reproduce output (focus error) I=0 of focus sensor FS, or morespecifically, so that the sectional shape of the reflected light ondetection surface ZD is in the form of a circle, as shown in FIG. 30D.Accordingly, measurement section ZE of Z head ZS outputs reading value Ecorresponding to the surface position of surface S of foreign materialDW as the measured value of Z head ZS.

Measured value E of Z head ZS at this point diverges greatly from thepredicted measurement value of Z head ZS corresponding to the predictedsurface position of measurement target surface S₀, or more specifically,from E₀. Therefore, offset Oz also becomes a large value. So, maincontroller 20 sets a threshold value for offset Oz, and when offset Ozexceeds the threshold value, main controller 20 decides that abnormalityhas occurred in the measurement results of Z head ZS and switches Z headZS from the operating state (focus servo state) to the waiting state(scale servo state). Main controller 20 stops updating offset Oz, afterswitching to the waiting state.

FIG. 30E shows Z head ZS just after being changed to the waiting state.In the waiting state, sensor main section ZH is driven by the drivesection (not shown) so that the focal point of probe beam LB follows thepredicted surface position of measurement target surface SD, or morespecifically, so that measurement section ZE outputs reading value E₀corresponding to the predicted surface position of measurement targetsurface S₀. At this point, the focal point of probe beam LB matches thepredicted surface position of measurement target surface S₀, and notsurface S of foreign material DW which is the actual reflection surface.Therefore, the cross section of the reflected light on detection surfaceZD becomes a non-circular shape, as shown in FIG. 30F. At this pointsfocus error I as expressed in formula (7) of the focus sensor FS is nolonger zero, (I≠zero).

After switching to the waiting state, focus error I (formula (7) offocus sensor FS is monitored. In the waiting state, because the focalpoint of probe beam LB deviates from the actual reflection surface(surface S of foreign material DW) as described above, output I≠0. Inthis case, if the focal point of probe beam LB returns onto the actualreflection surface, or if the actual reflection surface is displaced andthe surface position matches with the focal point of probe beam LB,output I also returns to zero. Accordingly, if output I returns to zeroin the waiting state where the focal point of probe beam LB follows thepredicted surface position of measurement target surface S₀, thisindicates that the surface position of the actual reflection surface hasmatched with the predicted surface position of measurement targetsurface S₀. Accordingly, it can be decided that the influence due todetecting foreign material DW has been resolved.

Therefore, when it has been confirmed that the cross section of thereflected light on detection surface ZD has returned to a circular shapeas shown in FIG. 30H, and output I of focus sensor FS has returned tozero or to approximately zero, main controller 20 switches Z head ZSfrom the waiting state (scale servo state) to the operating state (focusservo state) as shown in FIG. 30G. Main controller 20 then begins toupdate offset Oz again, after performing the switching to the operatingstate.

Incidentally, surface position information of measurement target surfaceS₀ cannot be taken out from Z head ZS in the waiting state. Therefore,main controller 20 predicts the measurement value of Z head ZS in thewaiting state from the measurement results of interferometer system 118,and by substituting the predicted value, computes the position (Z, θy)of wafer stage WST.

By the handling so that the individual Z heads in which the abnormalitydescribed above is generated are made to wait, it becomes possible toperform drive control of wafer stage WST without switching all the Zheads (surface position measurement system 180) to a different sensorsystem. Incidentally, the threshold value with respect to offset Ozdescribed above should be appropriately changed depending on the stateof exposure apparatus 100, such as, for example, at the time of startup, reset, and exposure. Further, as in the method which will bedescribed below, the entire Z heads (surface position measurement system180) can be switched to another sensor system.

When abnormality is detected in the measuring instrument system, such asthe output signal of Z heads 72 a to 72 d, 74 ₁ to 74 ₅, and 76 ₁ to 76₅ (refer to FIG. 6) of surface position measurement system 180 being cutoff, main controller 20 immediately performs a backup operation so as toswitch to a servo control of the position (Z, θy) of wafer stage WST byinterferometer system 118 (refer to FIG. 6) in order to prevent theservo control of the position (Z, θy) of wafer stage WST (wafer tableWTB) from stopping. More specifically, main controller 20 switches themeasuring instrument system used to compute the position coordinates ofwafer stage WST (water table WTB) from surface position measurementsystem 180 (Z heads 72 a to 72 d, 74 ₁ to 74 ₅, and 76 ₁ to 76 ₅) tointerferometer system 118. On this operation, a linkage process isperformed so that the position coordinates of wafer stage WST that havebeen computed are successive.

FIG. 31 is a view showing an outline of a linkage process in a switching(and a reversed switching) from servo control of the position (Z, θy) ofwafer stage WST by surface position measurement system 180 to servocontrol of the position (Z, θy) of wafer stage WST by interferometersystem 118.

First of all, main controller 20 per forms pre-processing for linkageprocess with respect to each control clock (CSCK). In this case, at thetime of the first measurement clock (MSCK) and the like shown in FIG.31, as shown by a solid black figure, the output signals of both thesurface position measurement system 180 and interferometer system 118are constantly monitored. However, in actual practice, the measurementclock of interferometer system 118 occurs more frequently than themeasurement clock of surface position measurement system 180, however,in this case, in order to avoid complication, only the measurement clockwhich occurs simultaneously is shown. At the time of control clockgeneration, main controller 20 computes the position coordinate (Z, θy)of wafer stage WST from the measurement result of Z heads (ZsL, ZsR)(hereinafter described as surface position measurement system (ZsL,ZsR)) of surface position measurement system 180 as in FIG. 31 at thetime of the first control clock generation, and also computes theposition coordinate (Z′, θy′) of wafer stage WST from the measurementresults of the interferometer system (IntZ) corresponding to the Zinterferometer of interferometer system 118. Then, main controller 20obtains the difference between the two position coordinates (Z, θy) and(Z′, θy′), and takes a moving average MA_(K) {(Z, θy)−(Z′, θy′)} for apredetermined clock number K, and keeps it as a coordinate offset O.However, in FIG. 31, the calculation of the differential moving averageis indicated by reference code MA.

As previously described, this coordinate offset O can be used also as anindex to judge the abnormality generation in the measurement results ofthe surface position measurement system (ZsL, ZsR). If an absolute valueof coordinate offset O is equal to or under a permissible value decidedbeforehand, main controller 20 will decide that no abnormality hasoccurred, and if the absolute value exceeds the permissible value, thenmain controller 20 will decide that abnormality has occurred. At thetime of the first control clock in FIG. 31, main controller 20 decidesthat no abnormality has occurred, therefore, uses the positioncoordinate (Z, θy) of wafer stage WST computed from the measurementresults of the surface position measurement system (ZsL, ZsR) as theposition coordinate used for the servo control of wafer stage WST.

On detecting the abnormality of the output signals of the surfaceposition measurement system (ZsL, ZsR), main controller 20 promptlyperforms the linkage process to the interferometer system. In this case,assume that at the time of the 1₃ clock in FIG. 31, abnormality occursin the output signals of the Z head system (ZsL, ZsR), such as forexample, the output signals being cut off. In FIG. 31, the state wherethe output signals are cut off is shown by an outlined figure.Incidentally, because scale servo previously described is possible withthe Z heads of the embodiment, the output signals actually are rarelycut off, however, in this case, to simplify the description, a case isillustrated where the output signals are cut off.

Then, main controller 20 adds the coordinate offset O kept in the firstcontrol clock just before to the position coordinate (Z′, θy′) of waferstage WST computed from the measurement results of the interferometersystem at the time of the second control clock, so that the positioncoordinate coincides with the position coordinate (Z, θy) of wafer stageWST computed from the measurement results of the surface positionmeasurement system (ZsL, ZsR) at the time of control clock (in thiscase, at the time of the first control clock) just before. Then, untilthe recovery of the output signal is detected, main controller 20performs the servo control of the position (Z, θy) of water stage WST,using the position coordinate [(Z′, θy′)+O] to which this offsetcancellation has been performed.

Incidentally, in FIG. 31, the output signals of two Z heads ZsL and ZsRwere cut off at the time of the 1₃ clock. As well as the two outputsignals, even in the case when one of the output signals is cut off,when the output signals supplied becomes one or less, the positioncoordinate of wafer stage WST cannot be computed using the theoreticalformulas (11) and (12), therefore, main controller 20 performs a similarswitching of the servo control of the position (Z, θy) of wafer stageWST.

And, on detecting the recovery of the output signals of the surfaceposition measurement system (ZsL, ZsR), main controller 20 promptlyperforms a reverse linkage process from the interferometer system 118 tothe surface position measurement system (ZsL, ZsR). In this case, assumethat the output signals of Z heads ZsL and ZsR are restored at the timeof the 2₃ clock in FIG. 31. At the time of the third control clock afterhaving detected the recovery, main controller 20 substitutes theposition coordinate [(Z′, θy′)+O] supplied from the interferometersystem to which offset cancellation has been applied into theoreticalformulas (9) and (10) and computes the measurement values that each ofthe Z heads ZsL and ZsR are to show, and performs initialization.However, in FIG. 31, this process is shown by reference code CH. Fromthe next fourth control clock onward, similar to the time of the firstclock, main controller 20 performs the usual servo control by thesurface position measurement system (ZsL, ZsR). At the same time, maincontroller 20 begins to update coordinate offset O again.

As a matter of course, not only in the case when the output signals fromthe Z heads are cut off as described above, main controller 20 performsa similar switching of the servo control of the position (Z, θy) ofwafer stage WST also in the case when the reliability of the outputsignals is low. In this case, main controller 20 secures the reliabilityof the output signals by using coordinate offset O previously describedas an index. At the time of the fifth control clock in FIG. 31, maincontroller 20 judges that the reliability has become less than apermissible level, and the position coordinate (Z′, θyY) of wafer stageWST computed from the measurement results of the interferometer systemis used as the position coordinate used for servo control. Incidentally,because coordinate offset O at this point of time is also unreliable,correction is to be performed using the latest coordinate offset O outof the coordinate offsets O which have been verified in the past. And,in the case when the reliability is sufficiently restored, the positioncoordinate (Z, θy) of wafer stage WST computed from the measurementresults of the surface position measurement system (ZsL, ZsR) is used asthe position coordinate used in servo control, similar to the time ofthe first and the fourth clocks.

When abnormality occurs in surface position measurement system 180, maincontroller 20 selects a suitable processing method according to thegeneration timing. As a processing method that can be performedfrequently, the following three methods are prepared. First of all, (a)an alert of abnormality generation is issued to a user, however, thecontrol is switched to a servo control of the position of wafer stageWST by interferometer system 118 by automatic operation withoutinterrupting the processing. (b) An alert is issued to a user, and theuser is requested to make a judgment such as, whether to continue theprocess believing that the backup operation has functioned normally, toswitch from the servo control of the position of wafer stage WST byinterferometer system 118 to the servo control according to surfaceposition measurement system 180 (Z heads 72 a to 72 d, 74 ₁ to 74 ₅, and76 ₁ to 76 ₅), to perform the focus calibration and the focus mappingall over again, or to cancel the process. (c) Perform automaticswitching of the servo control of the position of wafer stage WST,without issuing an alert. Method (a) should be applied at the time ofexposure, whereas method (b) should be applied at the time of focuscalibration and focus mapping. Incidentally, method (c) is to be appliedat the time of switching of the servo control of the position of waferstage WST from the control by surface position measurement system 180 (Zhead 72 a to 72 d, 74 ₁ to 74 ₅, and 76 ₁ to 76 ₅) described later on tothe control by interferometer system 118.

There is a case when main controller 20 switches to a servo control ofthe position of wafer stage WST by interferometer system 118 (refer toFIG. 6), besides the case described above when abnormality occurs in theZ heads 72 a to 72 d, 74 ₁ to 74 ₅, and 76 ₁ to 76 ₅ (refer to FIG. 6).As is previously described, encoder systems 70A to 70F, and Z heads 72 ato 72 d, 74 ₁ to 74 ₅, and 76 ₁ to 76 ₅ are placed to measure theposition coordinates of wafer stage WST (wafer table WTB) in theeffective stroke area of wafer stage WST, or more specifically, in thearea where the stage moves for alignment and exposure operation, and forfocus mapping. However, the areas where the stage moves for loading andunloading of the wafer shown in FIGS. 14 and 15 are not covered.Accordingly, when wafer stage WST is located at the loading/unloadingarea, servo control of the position of wafer stage WST by interferometersystem 118 is executed. Therefore, as shown in FIG. 16, when wafer stageWST passes over the effective stroke area and the loading/unloadingarea, main controller 20 performs the switching process of the servocontrol of position (X, Y, θz) and position (Z, θx) of wafer stage WST.

When wafer stage WST moves to the effective stroke area from theloading/unloading area to begin exposure, main controller 20 switchesfrom the servo control of position (X, Y, θz) of wafer stage WST byinterferometer system 118 to the servo control of position (X, Y, θz) ofwafer stage WST by encoder system 150. On this switching, maincontroller 20 switches from the servo control of position (Z, θy) ofwafer stage WST by interferometer system 118 to the servo control ofposition (Z, θy) of wafer stage WST by surface position measurementsystem 180. In this case, main controller 20 applies the coordinatelinkage method, and obtains predicted measurement values Z_(L) and Z_(R)which the two heads to be used should output by substituting positioncoordinate (Z, θx, θy) of wafer stage WST computed from the measurementresults of interferometer system 118 into theoretical formulas (9) and(10). Next, main controller 20 decides offsets OL and OR from thedifference between the predicted measurement value and the measuredvalue that has been obtained, and offsets OL and OR that have beendetermined are set with respect to two Z heads. This secures continuityof the position coordinate of wafer stage WST before and after theswitching. However, because the switching process is to be executed in astate where wafer stage WST (wafer table WTB) is suspended, thecontinuity of the position coordinate of wafer stage WST is notnecessarily required.

Meanwhile, when exposure has been completed and wafer stage WST movesfrom the loading/unloading area to the effective stroke area to exchangethe wafer, main controller 20 switches the servo control of the position(X, Y, θz) of wafer stage WST by encoder system 150 to the servo controlof the position (X, Y, θz) of wafer stage WST by interferometer system118. At this point, main controller 20 switches from the servo controlof position (Z, θy) of wafer stage WST by surface position measurementsystem 180 to the servo control of position (Z, θy) of wafer stage WSTby interferometer system 118. The procedure is basically similar to thebackup operation to switch to servo control by the interferometer systempreviously described. However, on the linkage process, the coordinateoffset is not used to dissolve the linkage error accumulated in eachswitching of the Z head. More specifically, the wafer table drivecontrol is performed using uncorrected position coordinates of waferstage WST that are obtained from the interferometer system.

However, when the coordinate offset grows large, or more specifically,the divergence between the measurement results of interferometer system118 and the measurement results of surface position measurement system180 grows large, the position coordinates of wafer stage WST which iscomputed before and after the switching become discontinuous, and aninconvenience may occur in the servo control of position (Z, θy) ofwafer stage WST. To avoid this, the following process can be carriedout. (a) After the exposure has been completed, when wafer stage WSTstops for the scrum state with measurement stage MST, the control isswitched to servo control of position (Z, θy) of wafer stage WST byinterferometer system 118. (b) Wafer stage WST moves to the unloadposition without performing an explicit switching process, and when theZ head output turns to be outside a predicted range (scale servo is notperformed at this point), the control is switched to servo control byinterferometer system 118. In the process above, as in the backupprocess by the interferometer system previously described, the linkagemethod using coordinate offset O is performed so that the positioncoordinates of wafer stage WST do not become discontinuous. Then, whenwafer stage WST stops, such as when the wafer is unloaded, the positioncoordinates of wafer stage WST are to be reset to uncorrected positioncoordinates obtained from interferometer system 118 without usingcoordinate offset O.

Incidentally, at the time of focus calibration and focus mapping, theswitching between the servo control of position (Z, θy) of wafer stageWST by Z heads 72 a to 72 d of surface position measurement system 180and the servo control of position (Z, θy) of wafer stage WST byinterferometer system 118 frequently occurs, due to the movement ofwafer stage WST in the X-axis direction. Therefore, by applying thecoordinate linkage method to servo control of position (Z, θy) of waferstage WST, position coordinates of wafer stage WST whose continuity hasbeen secured before and after the switching is used. And, for focuscalibration and focus mapping, position coordinates of wafer stage WSTobtained from the measured results of surface position measurementsystem 180 is used. This handling eliminates the influence that thelinkage error may have on focus calibration and focus mapping.

Incidentally, so far, in order to simplify the description, while maincontroller 20 performed the control of each part of the exposureapparatus including the control of the stage system (such as reticlestage RST and wafer stage WST), interferometer system 119, encodersystem 150, surface position measurement system 180 and the like, as amatter of course, at least a part of the control of main controller 20described above can be performed shared by a plurality of controllers.For example, a stage controller which performs operations such as thecontrol of the stage, switching of the heads of encoder system 150 andsurface position measurement system 180 can be arranged to operate undermain controller 20. Further, the control that main controller 20performs does not necessarily have to be realized by hardware, and maincontroller 20 can realize the control by software according to acomputer program that sets each operation of some controllers thatperform the control sharing as previously described.

As discussed in detail above, according to exposure apparatus 100 of theembodiment, main controller 20 drives wafer stage WST in the Z-axisdirection and the tilt direction (θy direction) with respect to the XYplaner based on measurement value (detection information) of surfaceposition measurement system 180, and also updates relation informationbetween a first positional information of wafer stage WST computed frommeasurement values (detection information) of surface positionmeasurement system 180 and a second positional information of waferstage WST computed from measurement values (detection information) ofinterferometer system 118 at every predetermined timing, and when maincontroller 20 detects that abnormality has occurred in the output ofsurface position measurement system 180, switches the detection deviceused for drive control (servo control of the position) of wager stageWST in the Z-axis direction and the tilt direction (θy direction) withrespect to the XY plane from surface position measurement system 180 tointerferometer system 118. Accordingly, backup according tointerferometer system 118, in which output abnormality is remarkablyhard to occur when compared with surface position measurement system 180from the measurement principle, becomes possible at the time ofgeneration of output abnormality in surface position measurement system180.

Further, according to exposure apparatus 100, on switching from servocontrol of the position related to the X, Y, and θz directions of wafertable WTB (wafer stage WST) using interferometer system 118 (Xinterferometer 128 and Y interferometer 16) to servo control of theposition related to the X, Y, and θz directions of wafer stage WST usingencoder system 150, when wafer stage WST is in a suspended state, maincontroller 20 switches the detection device which detects positionalinformation of wafer stage WST in the Z direction and θy direction frominterferometer system 118 (Z interferometers 43R and 43B) to surfaceposition measurement system 180. Further, on switching from servocontrol of the position related to the X, Y, and θz directions of waferstage WST using encoder system 150 to servo control of the positionrelated to the X, Y, and θz directions of wafer stage WST usinginterferometer system 118 (X interferometer 128 and Y interferometer16), at the point where wafer stage WST is suspended, main controller 20switches the detection device which detects positional information ofwafer stage WST in the Z direction and θy direction from surfaceposition measurement system 180 to interferometer system 118 (Zinterferometers 43A and 43B). Therefore, even if discontinuity occursbetween the position of wafer stage WST related to the X, Y, and θzdirections computed using detection information of surface positionmeasurement system 180 and the position of wafer stage WST related tothe X, Y, and θz directions computed using detection information ofinterferometer system 118 (Z interferometers 43A and 43B), switchingfrom interferometer system 118 (Z interferometers 43A and 43B) tosurface position measurement system 180 or switching in a reversed ordercan be performed without any trouble.

As described above, in exposure apparatus 100 related to the embodiment,normally, on operation which requires precision such as exposure andfocus napping, the position of wafer stage WST in the Z-axis directionand By direction is controlled with high precision using surfaceposition measurement system 180, and when abnormality has occurred inthe output of surface position measurement system 180, drive control ofwafer stage WST can be continued according to the backup ofinterferometer system 118.

Further, according to exposure apparatus 100 of the embodiment, bytransferring and forming the pattern of reticle R in each shot area onwafer W mounted on wafer stage WST (wafer table WTB) which is drivenwith good precision as described above, it becomes possible to form apattern with good precision in each shot area on wafer W. Furthersaccording to exposure apparatus 100 of the embodiment, by performing thefocus leveling control of the wafer with high accuracy during scanningexposure using the Z heads without measuring the surface positioninformation of the wafer W surface during exposure, based on the resultsof focus mapping performed beforehand, it becomes possible to form apattern on wafer W with good precision. Furthermore, in the embodiment,because a high-resolution exposure can be realized by liquid immersionexposure, a fine pattern can be transferred with good precision on waferW also from this viewpoint.

Incidentally, in the embodiment above, when focus sensor FS of each Zhead performs the focus-servo previously described, the focal point maybe on the cover glass surface protecting the diffraction grating surfaceformed on Y scales 39Y₁ and 39Y₂, however, it is desirable for the focalpoint to be on a surface further away than the cover glass surface, suchas, on the diffraction grating surface. With this arrangement, in thecase foreign material (dust) such as particles is on the cover glasssurface and the cover glass surface becomes a surface which is defocusedby the thickness of the cover glass, the influence of the foreignmaterial is less likely to affect the Z heads.

In the embodiment above, the surface position measurement system whichis configured having a plurality of Z heads arranged exterior to waferstage WST (the upper part) in the operating range (a range where thedevice moves in the actual sequence in the movement range) of waterstage WST and detects the Z position of the wafer table WTB (Y scales39Y₁ and 39Y₂) surface with each Z head was employed, however, thepresent invention is not limited to this. For example, a plurality of Zheads can be placed on the upper surface of a movable body (for example,wafer stage WST in the case of the embodiment above), and a detectiondevice, which faces the heads and has a reflection surface arrangedoutside the movable body that reflects the probe beam from the Z heads,can be employed, instead of surface position measurement system 180.

Further, in the embodiment above, an example has been described wherethe encoder system is employed that has a configuration where a gridsection (a Y scale and an X scale) is arranged on a wafer table (a waferstage), and X heads and Y heads facing the grid section are placedexternal to the wafer stage, however, the present invention is notlimited to this, and an encoder system which is configured having anencoder head arranged on the movable body and has a two-dimensional grid(or a linear grid section having a two-dimensional placement) facing theencoder heads placed external to the wafer stage can also be adopted. Inthis case, when Z heads are also to be placed on the movable body uppersurface, the two-dimensional grid (or the linear grid section having atwo-dimensional placement) can also be used as a reflection surface thatreflects the probe beam from the Z heads.

Further, in the embodiment above, the case has been described where eachZ head is equipped with sensor main section ZH (the first sensor) whichhouses focus sensor FS and is driven in the Z-axis direction by thedrive section (not shown), measurement section ZE (the second sensor)which measures the displacement of the first sensor (sensor main sectionZH) in the Z-axis direction, and the like as shown in FIG. 7, however,the present invention is not limited to this. More specifically, withthe Z head (the sensor head), the first sensor itself does notnecessarily have to be movable in the Z-axis direction, as long as apart of the member configuring the first sensor (for example, the focussensor previously described) is movable, and the part of the membermoves according to the movement of the movable body in the Z-axisdirection so that the optical positional relation (for example, aconjugate relation of the light receiving elements within the firstsensor with the photodetection surface (detection surface)) of the firstsensor with the measurement object surface is maintained. In such acase, the second sensor measures the displacement in the movementdirection from a reference position of the movable member. As a matterof course, in the case a sensor head is arranged on the movable body,the movable member should be moved so that the optical positionalrelation of the measurement object of the first sensor, such as, forexample, the two-dimensional grid described above (or the linear gridsection having a two-dimensional placement) and the like with the firstsensor is maintained, according to the position change of the movablebody in a direction perpendicular to the two-dimensional plane.

Further, in the embodiment above, while the case has been describedwhere the surface position of the measurement target surface is measuredin a focus servo control state, in which the Z head in a first controlstate, or more specifically, sensor main section ZH (the first sensor)which houses focus sensor FS as shown in FIG. 7 is driven in the Z-axisdirection by the drive section (not shown), and displacement in theZ-axis direction of the first sensor in this state is measured, usingmeasurement section ZE (the second sensor), the present invention is notlimited to this. More specifically, the surface position of themeasurement target surface can be measured in the scale servo controlstate where the position of the first sensor in the Z-axis direction iscontrolled according to the second control state, that is, themeasurement results of the second sensor, using the drive section (notshown), and the output signals (focus error I) of the first sensor aremeasured in such a state. In accordance with the same principle, insteadof the Z head, a Z head with the first sensor fixed, or a sensor headconfigured only from the first sensor and does not include the drivesection (not shown) and the second sensor can be used. Further, insteadof the Z head, as well as the focus sensor by an optical pickup method,a displacement sensor head which can measure the displacement of thesubject can be used.

Further, in the embodiment above, while the case has been describedwhere the encoder head and the Z head are separately arranged, besidessuch a case, for example, a head that has both functions of the encoderhead and the Z head can be employed, or an encoder head and a Z headthat have a part of the optical system in common can be employed, or acombined head which is integrated by arranging the encoder head and theZ head within the same housing can also be employed.

Incidentally, in the embodiment above, while the lower surface of nozzleunit 32 and the lower end surface of the tip optical element ofprojection optical system PL were on a substantially flush surface, aswell as this, for example, the lower surface of nozzle unit 32 can beplaced nearer to the image plane (more specifically, to the wafer) ofprojection optical system PL than the outgoing surface of the tipoptical element. That is, the configuration of local liquid immersionunit 8 is not limited to the configuration described above, and theconfigurations can be used, which are described in, for example, EPPatent Application Publication No. 1 420 298, the pamphlet ofInternational Publication No. 2004/055803, the pamphlet of InternationalPublication No. 2004/057590, the pamphlet of International PublicationNo. 2005/029559 (the corresponding U.S. Patent Application PublicationNo. 2006/0231206), the pamphlet of International Publication No.2004/086468 (the corresponding U.S. Patent Application Publication No.2005/0280791), the U.S. Pat. No. 6,952,253, and the like. Further, asdisclosed in the pamphlet of International Publication No. 2004/019128(the corresponding U.S. Patent Application Publication No.2005/0248856), the optical path on the object plane side of the tipoptical element may also be filled with liquid, in addition to theoptical path on the image plane side of the tip optical element.Furthermore, a thin film that is lyophilic and/or has dissolutionpreventing function may also be formed on the partial surface (includingat least a contact surface with liquid) or the entire surface of the tipoptical element. Incidentally, quartz has a high affinity for liquid,and also needs no dissolution preventing film, while in the case offluorite, at least a dissolution preventing film is preferably formed.

Incidentally, in the embodiment above, pure water (water) was used asthe liquid, however, it is a matter of course that the present inventionis not limited to this. As the liquid, liquid that is chemically stable,having high transmittance to illumination light IL and safe to use, suchas a fluorine-containing inert liquid may be used. As thefluorine-containing inert liquid, for example, Fluorinert (the brandname of 3M United States) can be used. The fluorine-containing inertliquid is also excellent from the point of cooling effect. Further, asthe liquid, liquid which has a refractive index higher than pure water(a refractive index is around 1.44), for example, liquid having arefractive index equal to or higher than 1.5 can be used. As this typeof liquid, for example, a predetermined liquid having C—H binding or O—Hbinding such as isopropanol having a refractive index of about 1.50,glycerol (glycerin) having a refractive index of about 1.61, apredetermined liquid (organic solvent) such as hexane, heptane ordecade, or decalin (decahydronaphthalene) having a refractive index ofabout 1.60, or the like can be cited. Alternatively, a liquid obtainedby mixing arbitrary two or more of these liquids may be used, or aliquid obtained by adding (mixing) at least one of these liquids to(with) pure water may be used. Alternatively, as the liquid, a liquidobtained by adding (mixing) base or acid such as H⁺, Cs⁺, K⁺, Cl⁻, SO₄²⁻, or PO₄ ²⁻ to (with) pure water can be used. Moreover, a liquidobtained by adding (mixing) particles of Al oxide or the like to (with)pure water can be used. These liquids can transmit ArF excimer laserlight. Further, as the liquid, liquid, which has a small absorptioncoefficient of light, is less temperature-dependent, and is stable to aprojection optical system (tip optical member) and/or a photosensitiveagent (or a protection film (top coat film), an antireflection film, orthe like) coated on the surface of a wafer, is preferable. Further, inthe case an F₂ laser is used as the light source, fomblin oil can beselected. Further, as the liquid, a liquid having a higher refractiveindex to illumination light IL than that of pure water, for example, arefractive index of around 1.6 to 1.8 may be used. As the liquid,supercritical fluid can also be used. Further, the tip optical elementof projection optical system PL may be formed by quartz (silica), orsingle-crystal materials of fluoride compound such as calcium fluoride(fluorite), barium fluoride, strontium fluoride, lithium fluoride, andsodium fluoride, or may be formed by materials having a higherrefractive index than that of quartz or fluorite (e.g. equal to orhigher than 1.6). As the materials having a refractive index equal to orhigher than 1.6, for example, sapphire, germanium dioxide, or the likedisclosed in the pamphlet of International Publication No. 2005/059617,or kalium chloride (having a refractive index of about 1.75) or the likedisclosed in the pamphlet of International Publication No 2005/059618can be used.

Further, in the embodiment above, the recovered liquid may be reused,and in this case, a filter that removes impurities from the recoveredliquid is preferably arranged in a liquid recovery unit, a recovery pipeor the like.

Incidentally, in the embodiment above, the case has been described wherethe exposure apparatus is a liquid immersion type exposure apparatus.However, the present invention is not limited to this, but can also beemployed in a dry type exposure apparatus that performs exposure ofwafer W without liquid (water).

Further, in the embodiment above, the case has been described where thepresent invention is applied to a scanning exposure apparatus by astep-and-scan method or the like. However, the present invention is notlimited to this, but may also be applied to a static exposure apparatussuch as a stepper. Further, the present invention can also be applied toa reduction projection exposure apparatus by a step-and-stitch methodthat synthesizes a shot area and a shot area, an exposure apparatus by aproximity method, a mirror projection aligner, or the like. Moreover,the present invention can also be applied to a multi-stage type exposureapparatus equipped with a plurality of wafer stage WSTs, as is disclosedin, for example, the U.S. Pat. No. 6,590,634, the U.S. Pat. No.5,969,441, the U.S. Pat. No. 6,208,407 and the like.

Further, the magnification of the projection optical system in theexposure apparatus of the embodiment above is not only a reductionsystem, but also may be either an equal magnifying system or amagnifying system, and projection optical system PL is not only adioptric system, but also may be either a catoptric system or acatodioptric system, and in addition, the projected image may be eitheran inverted image or an upright image. Moreover, exposure area IA towhich illumination light IL is irradiated via projection optical systemPL is an on-axis area that includes optical axis AX within the field ofprojection optical system PL. However, for example, as is disclosed inthe pamphlet of International Publication No. 2004/107011, exposure areaIA may also be an off-axis area that does not include optical axis AX,similar to a so-called inline type catodioptric system, in part of whichan optical system (catoptric system or catodioptric system) that hasplural reflection surfaces and forms an intermediate image at least onceis arranged, and which has a single optical axis. Further, theillumination area and exposure area described above are to have arectangular shape. However, the shape is not limited to rectangular, andcan also be circular arc, trapezoidal, parallelogram or the like.

Incidentally, a light source of the exposure apparatus in the embodimentabove is not limited to the ArF excimer laser, but a pulse laser lightsource such as a KrF excimer laser (output wavelength: 248 nm), an F₂laser (output wavelength: 157 nm), an Ar₂ laser (output wavelength: 126nm) or a Kr₂ laser (output wavelength: 146 nm), or an extra-highpressure mercury lamp that generates an emission line such as a g-line(wavelength: 436 nm) or an i-line (wavelength: 365 nm) can also be used.Further, a harmonic wave generating unit of a YAG laser or the like canalso be used. Besides the sources above, as is disclosed in, forexample, the pamphlet of International Publication No. 1999/46835 (thecorresponding U.S. Pat. No. 7,023,610), a harmonic wave, which isobtained by amplifying a single-wavelength laser beam in the infrared orvisible range emitted by a DFB semiconductor laser or fiber laser asvacuum ultraviolet light, with a fiber amplifier doped with, forexample, erbium (or both erbium and ytterbium), and by converting thewavelength into ultraviolet light using a nonlinear optical crystal, canalso be used.

Further, in the embodiment above, illumination light IL of the exposureapparatus is not limited to the light having a wavelength equal to ormore than 100 nm, and it is needless to say that the light having awavelength less than 100 nm can be used. For example, in recent years,in order to expose a pattern equal to or less than 70 nm, an EUVexposure apparatus that makes an SOR or a plasma laser as a light sourcegenerate an EUV (Extreme Ultraviolet) light in a soft X-ray range (e.g.a wavelength range from 5 to 15 nm) and uses a total reflectionreduction optical system designed under the exposure wavelength (forexample, 13.5 nm) and the reflective mask has been developed. In the EUVexposure apparatus, the arrangement in which scanning exposure isperformed by synchronously scanning a mask and a wafer using a circulararc illumination can be considered, and therefore, the present inventioncan also be suitably applied to such an exposure apparatus. Besides suchan apparatus, the present invention can also be applied to an exposureapparatus that uses charged particle beams such as an electron beam oran ion beam.

Further, in the embodiment above, a transmissive type mask (reticle) isused, which is a transmissive substrate on which a predetermined lightshielding pattern (or a phase pattern or a light attenuation pattern) isformed. Instead of this reticle, however, as is disclosed in, forexample, U.S. Pat. No. 6,778,257, an electron mask (which is also calleda variable shaped mask, an active mask or an image generator, andincludes, for example, a DMD (Digital Micromirror Device) that is a typeof a non-emission type image display device (spatial light modulator) orthe like) on which a light-transmitting pattern, a reflection pattern,or an emission pattern is formed according to electronic data of thepattern that is to be exposed can also be used.

Further, as is disclosed in, for example, the pamphlet of InternationalPublication No. 2001/035168, the present invention can also be appliedto an exposure apparatus (lithography system) that forms line-and-spacepatterns on a wafer by forming interference fringes on the wafer.

Moreover, as disclosed in, for example, U.S. Pat. No. 6,611,316, thepresent invention can also be applied to an exposure apparatus thatsynthesizes two reticle patterns via a projection optical system andalmost simultaneously performs double exposure of one shot area by onescanning exposure.

Further, an apparatus that forms a pattern on an object is not limitedto the exposure apparatus (lithography system) described above, and forexample, the present invention can also be applied to an apparatus thatforms a pattern on an object by an ink-jet method.

Incidentally, an object on which a pattern is to be formed (an objectsubject to exposure to which an energy beam is irradiated) in theembodiment above is not limited to a wafer, but may be other objectssuch as a glass plate, a ceramic substrate, a film member, or a maskblank.

The use of the exposure apparatus is not limited only to the exposureapparatus for manufacturing semiconductor devices, but the presentinvention can also be widely applied, for example, to an exposureapparatus for transferring a liquid crystal display device pattern ontoa rectangular glass plate, and an exposure apparatus for producingorganic ELs, thin-film magnetic heads, imaging devices (such as CCDs),micromachines, DNA chips, and the like. Further, the present inventioncan be applied not only to an exposure apparatus for producingmicrodevices such as semiconductor devices, but can also be applied toan exposure apparatus that transfers a circuit pattern onto a glassplate or silicon wafer to produce a mask or reticle used in a lightexposure apparatus, an EUV exposure apparatus, an X-ray exposureapparatus, an electron-beam exposure apparatus, and the like.

Incidentally, the movable body drive system and the movable body drivemethod of the present invention can be applied not only to the exposureapparatus, but can also be applied widely to other substrate processingapparatuses (such as a laser repair apparatus, a substrate inspectionapparatus and the like), or to apparatuses equipped with a movable bodysuch as a stage that moves within a two-dimensional plane such as aposition setting apparatus of a sample or a wire bonding apparatus inother precision machines.

Incidentally, the disclosures of the various publications(descriptions), the pamphlets of the International Publications, and theU.S. patent application Publication descriptions and the U.S. patentdescriptions that are cited in the embodiment above and related toexposure apparatuses and the like are each incorporated herein byreference.

Semiconductor devices are manufactured through the following steps: astep where the function/performance design of the wafer is performed, astep where a wafer is made using silicon materials, a lithography stepwhere the pattern formed on the reticle (mask) by the exposure apparatus(pattern formation apparatus) in the embodiment previously described istransferred onto a wafer, a development step where the wafer that hasbeen exposed is developed, an etching step where an exposed member of anarea other than the area where the resist remains is removed by etching,a resist removing step where the resist that is no longer necessary whenetching has been completed is removed, a device assembly step (includingprocesses such as a dicing process, a bonding process, and a packagingprocess), inspection steps and the like.

By using the device manufacturing method of the embodiment describedabove, because the exposure apparatus (pattern formation apparatus) inthe embodiment above and the exposure method (pattern formation method)thereof are used in the exposure step, exposure with high throughput canbe performed while maintaining the high overlay accuracy. Accordingly,the productivity of highly integrated microdevices on which finepatterns are formed can be improved.

While the above-described embodiment of the present invention is thepresently preferred embodiment thereof, those skilled in the art oflithography systems will readily recognize that numerous additions,modifications, and substitutions may be made to the above-describedembodiment without departing from the spirit and scope thereof. It isintended that all such modifications, additions, and substitutions fallwithin the scope of the present invention, which is best defined by theclaims appended below.

1. A movable body drive method in which a movable body is drivensubstantially along a two-dimensional plane, the method comprising: afirst process in which positional information of the movable bodyrelated to at least one of a direction perpendicular to thetwo-dimensional plane and a tilt direction with respect to thetwo-dimensional plane is detected, using a first detection device thathas one, or more than one detection positions placed in at least a partof an operating area of the movable body, and detects positionalinformation of the movable body in the direction perpendicular to thetwo-dimensional plane using detection information detected when themovable body is positioned at any one of the detection points, and asecond detection device that detects positional information of themovable body in the direction perpendicular to the two-dimensional planefrom measurement results using a measurement beam irradiated along thetwo-dimensional plane between the outside of the operating area of themovable body and the movable body, and the movable body is driven in atleast one of the direction perpendicular to the two-dimensional planeand the tilt direction with respect to the two-dimensional plane basedon detection results of the first detection device; a second process inwhich relation information between a first positional information of themovable body computed from detection information of the first detectiondevice and a second positional information of the movable body computedfrom detection in formation of the second detection device is updated atevery predetermined timing; and a third process in which whenabnormality occurring in an output of the first detection device hasbeen detected, the detection device used for drive control of themovable body in at least one of the direction perpendicular to thetwo-dimensional plane and the tilt direction with respect to thetwo-dimensional plane is switched from the first detection device to thesecond detection device.
 2. The movable body drive method according toclaim 1 wherein in the third process, the detection devices is switchedfrom the first detection device to the second detection device whosesecond position coordinate has been corrected, so that the secondposition coordinate of the movable body in an n^(th) order coordinatesystem computed from detection information of the first detection devicejust before becomes successive to a first position coordinate computedfrom the detection information of the movable body in at least adirection of one degree of freedom in the n^(th) order coordinate system(n is a natural number of three or less), among a directionperpendicular to the two-dimensional plane and rotational directionsaround two axes orthogonal to the two-dimensional plane.
 3. The movablebody drive method according to claim 2 wherein the relation informationis offset information associated with a difference between the firstposition coordinate and the second position coordinate of the movablebody.
 4. The movable body drive method according to claim 3 wherein therelation information is a moving average regarding a predeterminednumber of control clocks of the difference.
 5. The movable body drivemethod according to claim 1, the method further comprising: aninspection process in which reliability of the detection information ofthe first detection device is inspected, using the relation information.6. The movable body drive method according to claim 5 wherein in thethird process, when abnormality that has occurred in the output of thefirst detection device has been detected, the second positionalinformation of the movable body computed by the detection information ofthe second detection device at the time of occurrence is corrected,using the relation information which has been confirmed normal at thetime of a preceding inspection.
 7. The movable body drive methodaccording to claim 1, the method further comprising: a return process inwhich the detection device used for drive control of the movable body inat least one of the direction perpendicular to the two-dimensional planeand the tilt direction with respect to the two-dimensional plane isreturned from the second detection device to the first detection deviceat a predetermined timing, when the movable body is driven in at leastone of the direction perpendicular to the two-dimensional plane and thetilt direction with respect to the two-dimensional plane based on thedetection results of the second detection device.
 8. The movable bodydrive method according to claim 7 wherein reliability of the detectioninformation of the first detection device is inspected using therelation information, and as a result of the inspection, when thereliability has been confirmed, return from the second detection deviceto the first detection device is performed.
 9. The movable body drivemethod according to claim 1 wherein the abnormality is absence of outputfrom the first detection device, or the output from the first detectiondevice exceeding a predetermined threshold value.
 10. The movable bodydrive method according to claim 1 wherein as the first detection device,a detection device is used that has a plurality of sensor headsdetecting positional information of a surface of the movable bodysubstantially parallel to the two-dimensional plane in a directionperpendicular to the two-dimensional plane, with a reference planeparallel to the two-dimensional plane serving as a reference, when themovable body is positioned at each detection position in a plurality ofdifferent detection positions within an operating area of the movablebody, and each sensor head includes a first sensor including a movablemember which moves to maintain an optical positional relation with ameasurement subject according to a positional change of the movablemember in the direction perpendicular to the two-dimensional plane whenthe surface of the movable body is located at each detection position,and a second sensor which detects the displacement of the movable memberfrom a reference point.
 11. A pattern formation method to form a patternon an object wherein a movable body on which the object is mounted isdriven using the movable body drive method according to claim 1 toperform pattern formation to the object.
 12. The pattern formationmethod according to claim 11 wherein the object has a sensitive layer,and a pattern is formed on the object by an exposure of the sensitivelayer by irradiation of an energy beam.
 13. A device manufacturingmethod including a pattern formation process wherein in the patternformation process, a pattern is formed on a substrate using the patternformation method according to claim
 11. 14. An exposure method in whicha pattern is formed on an object by an irradiation of an energy beamwherein for relative movement of the energy beam and the object, amovable body on which the object is mounted is driven, using the movablebody drive method according to claim
 1. 15. A movable body drive methodin which a movable body is driven substantially along a two-dimensionalplane, the method comprising: a first process in which positionalinformation of the movable body in directions of three degrees offreedom within a plane parallel to the two-dimensional plane isdetected, using a first detection device which detects positionalinformation in directions of three degrees of freedom within the planeparallel to the two-dimensional plane from measurement results using ameasurement beam irradiated along the two-dimensional plane between theoutside of the operating area of the movable body and the movable body,and positional information of the movable body in a directionperpendicular to the two-dimensional plane and a tilt direction withrespect to the two-dimensional plane is also detected, using a seconddetection device which detects positional information of the movablebody in a direction perpendicular to the two-dimensional plane and atilt direction with respect to the two-dimensional plane frommeasurement results using a measurement beam irradiated along thetwo-dimensional plane between the outside of the operating area of themovable body and the movable body; and a second process in which onswitching from servo control of the position in the directions of threedegrees of freedom of the movable body using the first detection deviceto servo control of the position in the directions of three degrees offreedom of the movable body using an encoder system, a detection devicethat detects positional information of the movable body in the directionperpendicular to the two-dimensional plane and the tilt direction aroundat least one axis with respect to the two-dimensional plane is switchedfrom the second detection device when the movable body is in a suspendedstate, to a third detection device that has a plurality of detectionpositions placed in at least a part of an operating area of the movablebody, and detects positional information of the movable body in thedirection perpendicular to the two-dimensional plane using detectioninformation detected when the movable body is positioned at any one ofthe detection positions.
 16. The movable body drive method according toclaim 15 wherein as the third detection device, a detection device isused that has a plurality of sensor heads detecting positionalinformation of a surface of the movable body substantially parallel tothe two-dimensional plane in a direction perpendicular to thetwo-dimensional plane, with a reference plane parallel to thetwo-dimensional plane serving as a reference, when the movable body ispositioned at each detection position in a plurality of differentdetection positions within an operating area of the movable body, andeach sensor head includes a first sensor including a movable memberwhich moves to maintain an optical positional relation with ameasurement subject according to a positional change of the movablemember in the direction perpendicular to the two-dimensional plane whenthe surface of the movable body is located at each detection position,and a second sensor which detects the displacement of the movable memberfrom a reference point.
 17. A pattern formation method to form a patternon an object wherein a movable body on which the object is mounted isdriven using the movable body drive method according to claim 15 toperform pattern formation to the object.
 18. The pattern formationmethod according to claim 17 wherein the object has a sensitive layer,and a pattern is formed on the object by an exposure of the sensitivelayer by irradiation of an energy beam.
 19. A device manufacturingmethod including a pattern formation process wherein in the patternformation process, a pattern is formed on a substrate using the patternformation method according to claim
 17. 20. An exposure method in whicha pattern is formed on an object by an irradiation of an energy beamwherein for relative movement of the energy beam and the object, amovable body on which the object is mounted is driven, using the movablebody drive method according to claim
 15. 21. A movable body drive methodin which a movable body is driven substantially along a two-dimensionalplane, the method comprising: a first process in which the movable bodyis driven based on an output of a first detection device that has aplurality of detection positions placed in at least a part of anoperating area of the movable body, and detects positional informationof the movable body in a direction perpendicular to the two-dimensionalplane using detection information detected when the movable body ispositioned at any one of the detection positions, and the output of anencoder system that measures positional information of the movable bodywithin a plane parallel to the two-dimensional plane in directions ofthree degrees of freedom; and a second process in which in the case ofswitching from servo control of the position of the movable body in thedirections of three degrees of freedom using the encoder system, to acontrol of the position of the movable body in the directions of threedegrees of freedom using a second detection device that detectspositional information in directions of three degrees of freedom withina plane parallel to the two-dimensional plane from measurement resultsusing a measurement beam irradiated along the two-dimensional planebetween the outside of the operating are of the movable body and themovable body, a detection device used for control of the position of themovable body in the remaining directions of three degrees of freedom isswitched from the first detection device to a third detection devicethat detects positional information of the movable body in the directionperpendicular to the two-dimensional plane and a tilt direction withrespect to the two-dimensional plane from measurement results using ameasurement beam irradiated along the two-dimensional plane between theoutside of the operating area of the movable body and the movable bodyat the point where the movable body is suspended.
 22. The movable bodydrive method according to claim 21 wherein as the first detectiondevice, a detection device is used that has a plurality of sensor headsdetecting positional information of a surface of the movable bodysubstantially parallel to the two-dimensional plane in a directionperpendicular to the two-dimensional planer with a reference planeparallel to the two-dimensional plane serving as a reference, when themovable body is positioned at each detection position in a plurality ofdifferent detection positions within an operating area of the movablebody, and each sensor head includes a first sensor including a movablemember which moves to maintain an optical positional relation with ameasurement subject according to a positional change of the movablemember in the direction perpendicular to the two-dimensional plane whenthe surface of the movable body is located at each detection position,and a second sensor which detects the displacement of the movable memberfrom a reference point.
 23. The movable body drive method according toclaim 21 wherein the first detection device has a plurality of sensorheads detecting positional information of a surface of the movable bodysubstantially parallel to the two-dimensional plane in a directionperpendicular to the two-dimensional plane, with a reference planeparallel to the two-dimensional plane serving as a reference, when themovable body is positioned at each detection position in a plurality ofdifferent detection positions within an operating area of the movablebody, and each sensor head includes a first sensor including a movablemember which moves to maintain an optical positional relation with ameasurement subject according to a positional change of the movablemember in the direction perpendicular to the two-dimensional plane whenthe surface of the movable body is located at each detection position,and a second sensor which detects the displacement of the movable memberfrom a reference point.
 24. A pattern formation method to form a patternon an object wherein a movable body on which the object is mounted isdriven using the movable body drive method according to claim 21 toperform pattern formation to the object.
 25. The pattern formationmethod according to claim 24 wherein the object has a sensitive layer,and a pattern is formed on the object by an exposure of the sensitivelayer by irradiation of an energy beam.
 26. A device manufacturingmethod including a pattern formation process wherein in the patternformation process, a pattern is formed on a substrate using the patternformation method according to claim
 24. 27. An exposure method in whicha pattern is formed on, an object by an irradiation of an energy beamwherein for relative movement of the energy beam and the object, amovable body on which the object is mounted is driven, using the movablebody drive method according to claim
 21. 28. A movable body drive systemin which a movable body is driven substantially along a two-dimensionalplane, the system comprising: a first detection device that has ones ormore than one detection positions placed in at least a part of anoperating area of the movable body, and detects positional informationof the movable body in a direction perpendicular to the two-dimensionalplane using detection information detected when the movable body ispositioned at any one of the detection points; a second detection devicethat detects positional information of the movable body in the directionperpendicular to the two-dimensional plane from measurement resultsusing a measurement beam irradiated along the two-dimensional planebetween the outside of the operating area of the movable body and themovable body; and a controller that drives the movable body at least oneof a direction perpendicular to the two-dimensional plane and a tiltdirection with respect to the two-dimensional plane based on detectionresults of the first detection device, and also updates relationinformation between a first positional information of the movable bodycomputed from detection information of the first detection device and asecond positional information of the movable body computed fromdetection information of the second detection device at everypredetermined timing, and when abnormality occurring in the output ofthe first detection device is detected, switches a detection device usedfor drive control of at least one of the direction perpendicular to thetwo-dimensional plane and a tilt direction with respect to thetwo-dimensional plane from the first detection device to the seconddetection device.
 29. The movable body drive system according to claim28 wherein the controller performs switching from the first detectiondevice to the second detection device whose second position coordinatehas been corrected, so that the second position coordinate of themovable body in an n^(th) order coordinate system computed fromdetection information of the first detection device just before becomessuccessive to a first position coordinate computed from the detectioninformation of the movable body in at least a direction of one degree offreedom in the n^(th) order coordinate system (n is a natural number ofthree or less), among a direction perpendicular to the two-dimensionalplane and rotational directions around two axes orthogonal to thetwo-dimensional plane.
 30. The movable body drive system according toclaim 29 wherein the relation information is offset informationassociated with a difference between the first position coordinate andthe second position coordinate of the movable, body.
 31. The movablebody drive system according to claim 30 wherein the relation informationis a moving average regarding a predetermined number of control clocksof the difference.
 32. The movable body drive system according to claim28 wherein the controller inspects reliability of the detectioninformation of the first detection device, using the relationinformation.
 33. The movable body drive system according to claim 32wherein when abnormality that has occurred in the output of the firstdetection device has been detected, the controller corrects the secondpositional information of the movable body computed by the detectioninformation of the second detection device at the time of occurrence,using the relation information which has been confirmed normal at thetime of a preceding inspection.
 34. The movable body drive systemaccording to claim 28 wherein the controller returns the detectiondevice used for drive control of the movable body in at least one of thedirection perpendicular to the two-dimensional plane and the tiltdirection with respect to the two-dimensional plane from the seconddetection device to the first detection device at a predeterminedtiming, when the movable body is driven in at least one of the directionperpendicular to the two-dimensional plane and the tilt direction withrespect to the two-dimensional plane based on the detection results ofthe second detection device.
 35. The movable body drive system accordingto claim 34 wherein the controller inspects reliability of the detectioninformation of the first detection device using the relationinformation, and as a result of the inspection, when the reliability hasbeen confirmed, performs return from the second detection device to thefirst detection device.
 36. The movable body drive system according toclaim 28 wherein the abnormality is absence of output from the firstdetection device, or the output from the first detection deviceexceeding a predetermined threshold value.
 37. The movable body drivesystem according to claim 28 wherein the first detection device has aplurality of sensor heads detecting positional information of a surfaceof the movable body substantially parallel to the two-dimensional planein a direction perpendicular to the two-dimensional plane, with areference plane parallel to the two-dimensional plane serving as areference, when the movable body is positioned at each detectionposition in a plurality of different detection positions within anoperating area of the movable body, and each sensor head includes afirst sensor including a movable member which moves to maintain anoptical positional relation with a measurement subject according to apositional change of the movable member in the direction perpendicularto the two-dimensional plane when the surface of the movable body islocated at each detection position, and a second sensor which detectsthe displacement of the movable member from a reference point.
 38. Apattern forming apparatus that forms a pattern on an object, theapparatus comprising: a patterning device which generates a pattern onthe object; and a movable body drive system according to claim 29,wherein drive of a movable body on which the object is mounted isperformed by the movable body drive system for pattern formation withrespect to the object.
 39. The pattern formation apparatus according toclaim 38 wherein the object has a sensitive layer, and the patterningdevice generates a pattern on the object by an exposure of the sensitivelayer by irradiation of an energy beam.
 40. An exposure apparatus thatforms a pattern on an object by an irradiation of an energy beam, theapparatus comprising: a patterning device that irradiates the energybeam on the object; and a movable body drive system according to claim28, wherein the movable body drive system drives the movable body onwhich the object is mounted for relative movement of the energy beam andthe object.
 41. A movable body drive system in which a movable body isdriven along a substantially two-dimensional plane, the systemcomprising: a first detection device that has a plurality of detectionpositions placed in at least a part of an operating area of the movablebody, and detects positional information of the movable body in adirection perpendicular to the two-dimensional plane using detectioninformation detected when the movable body is positioned at any one ofthe detection points; an encoder system that measures positionalinformation of the movable body in directions of three degrees offreedom; a second detection device that detects positional informationof the movable body in directions of three degrees of freedom within aplane parallel to the two-dimensional plane from measurement resultsusing a measurement beam irradiated along the two-dimensional planebetween the outside of the operating area of the movable body and themovable body; a third detection device that detects positionalinformation of the movable body in a direction perpendicular to thetwo-dimensional plane and a tilt direction with respect to thetwo-dimensional plane from measurement results using a measurement beamirradiated along the two-dimensional plane between the outside of theoperating area of the movable body and the movable body; and acontroller that switches a detection device which detects positionalinformation of the movable body in the direction perpendicular to thetwo-dimensional plane and the tilt direction around at least one axiswith respect to the two-dimensional plane from the third detectiondevice when the movable body is in a suspended state to the firstdetection device, on switching from servo control of the position in thedirections of three degrees of freedom of the movable body using thesecond detection device to servo control of the position in thedirections of three degrees of freedom of the movable body using theencoder system.
 42. The movable body drive system according to claim 41wherein the first detection device includes a first sensor which has aplurality of sensor heads detecting positional information of a surfaceof the movable body substantially parallel to the two-dimensional planein a direction perpendicular to the two-dimensional plane, with areference plane parallel to the two-dimensional plane serving as areference when the movable body is positioned at each detection positionin a plurality of different detection positions within an operating areaof the movable body, and each sensor head including a movable memberthat moves to maintain an optical positional relation with a measurementsubject according to a positional change of the movable body in thedirection perpendicular to the two-dimensional plane when the surface ofthe movable body is located at each detection position, and a secondsensor which detects the displacement of the movable member from areference point.
 43. A pattern forming apparatus that forms a pattern onan object, the apparatus comprising: a patterning device which generatesa pattern on the object; and a movable body drive system according toclaim 42, wherein drive of a movable body on which the object is mountedis performed by the movable body drive system for pattern formation withrespect to the object.
 44. The pattern formation apparatus according toclaim 43 wherein the object has a sensitive layer, and the patterningdevice generates a pattern on the object by an exposure of the sensitivelayer by irradiation of an energy beam.
 45. An exposure apparatus thatforms a pattern on an object by an irradiation of an energy beam, theapparatus comprising: a patterning device that irradiates the energybeam on the object; and a movable body drive system according to claim41, wherein the movable body drive system drives the movable body onwhich the object is mounted for relative movement of the energy beam andthe object.
 46. A movable body drive system in which a movable body isdriven along a substantially two-dimensional plane, the systemcomprising: a first detection device that has a plurality of detectionpositions placed in at least a part of an operating area of the movablebody, and detects positional information of the movable body in adirection perpendicular to the two-dimensional plane using detectioninformation detected when the movable body is positioned at any one ofthe detection points; an encoder system that measures positionalinformation of the movable body within a plane parallel to thetwo-dimensional plane in directions of three degrees of freedom; asecond detection device that detects positional information of themovable body in directions of three degrees of freedom within a planeparallel to the two-dimensional plane from measurement results using ameasurement beam irradiated along the two-dimensional plane between theoutside of the operating area of the movable body and the movable body;a third detection device that detects positional information of themovable body in a direction perpendicular to the two-dimensional planeand a tilt direction with respect to the two-dimensional plane frommeasurement results using a measurement beam irradiated along thetwo-dimensional plane between the outside of the operating area of themovable body and the movable body; and a controller that switches ameasurement device used for controlling the position of the movable bodyin the remaining directions of three degrees of freedom from the firstdetection device to the third detection device at the point where themovable body is suspended, in the case of switching from servo controlof the position of the movable body using the encoder system to controlof the position of the movable body in the directions of three degreesof freedom using the second detection device.
 47. The movable body drivesystem according to claim 46 wherein the first detection device has aplurality of sensor heads detecting positional information of a surfaceof the movable body substantially parallel to the two-dimensional planein a direction perpendicular to the two-dimensional plane, with areference plane parallel to the two-dimensional plane serving as areference, when the movable body is positioned at each detectionposition in a plurality of different detection positions within anoperating area of the movable body, and each sensor head includes afirst sensor including a movable member which moves to maintain anoptical positional relation with a measurement subject according to apositional change of the movable member in the direction perpendicularto the two-dimensional plane when the surface of the movable body islocated at each detection position, and a second sensor which detectsthe displacement of the movable member from a reference point.
 48. Apattern forming apparatus that forms a pattern on an object, theapparatus comprising: a patterning device which generates a pattern onthe object; and a movable body drive system according to claim 46,wherein drive of a movable body on which the object is mounted isperformed by the movable body drive system for pattern formation withrespect to the object.
 49. The pattern formation apparatus according toclaim 48 wherein the object has a sensitive layer, and the patterningdevice generates a pattern on the object by an exposure of the sensitivelayer by irradiation of an energy beam.
 50. An exposure apparatus thatforms a pattern on an object by an irradiation of an energy beam, theapparatus comprising: a patterning device that irradiates the energybeam on the object; and a movable body drive system according to claim46, wherein the movable body drive system drives the movable body onwhich the object is mounted for relative movement of the energy beam andthe object.